I have to write searching algorithm, For example I have to compare str="giorgi" to str2="grigol". I'm trying to find longest matching sequence of chars, so that the order of chars is the same and string which I should get is "grg"... with this c# code I'm getting "grig".
int k=0;
string s="";
string str = "giorgi";
string str2 = "grigol";
for(int i=0;i<str.Length;i++)
{
for (int j = k; j < str2.Length; j++)
{
if (str[i] == str2[j])
{
s += str2[k];
k++;
goto endofloop;
}
}
endofloop:;
}
Console.WriteLine(s);
The solution:
using System;
class GFG
{
/* Returns length of LCS for X[0..m-1], Y[0..n-1] */
static int lcs( char[] X, char[] Y, int m, int n )
{
int [,]L = new int[m+1,n+1];
/* Following steps build L[m+1][n+1]
in bottom up fashion. Note
that L[i][j] contains length of
LCS of X[0..i-1] and Y[0..j-1] */
for (int i = 0; i <= m; i++)
{
for (int j = 0; j <= n; j++)
{
if (i == 0 || j == 0)
L[i, j] = 0;
else if (X[i - 1] == Y[j - 1])
L[i, j] = L[i - 1, j - 1] + 1;
else
L[i, j] = GFG.max(L[i - 1, j], L[i, j - 1]);
}
}
return L[m, n];
}
static int max(int a, int b)
{
return (a > b)? a : b;
}
}
And now the program to test it:
public static void Main()
{
String s1 = "giorgi";
String s2 = "grigol";
char[] X=s1.ToCharArray();
char[] Y=s2.ToCharArray();
int m = X.Length;
int n = Y.Length;
Console.Write("Length of LCS is" + " " +lcs( X, Y, m, n ) );
}
}
I have two words,
britanicaeng and
britanicahin
I need to find out the longest common word between these i.e, britanica.
How can I do this in C# ?
Try this method:
public static string FindLongestCommonSubstring(string s1, string s2)
{
int[,] a = new int[s1.Length + 1, s2.Length + 1];
int row = 0; // s1 index
int col = 0; // s2 index
for (var i = 0; i < s1.Length; i++)
for (var j = 0; j < s2.Length; j++)
if (s1[i] == s2[j])
{
int len = a[i + 1, j + 1] = a[i, j] + 1;
if (len > a[row, col])
{
row = i + 1;
col = j + 1;
}
}
return s1.Substring(row - a[row, col], a[row, col]);
}
Usage example:
Console.WriteLine(FindLongestCommonSubstring("britanicaeng", "britanicahin"));
I refactored the C++ code from Ashutosh Singh at https://iq.opengenus.org/longest-common-substring-using-rolling-hash/ to create a rolling hash approach in C# - this will find the substring in O(N * log(N)^2) time and O(N) space
using System;
using System.Collections.Generic;
public class RollingHash
{
private class RollingHashPowers
{
// _mod = prime modulus of polynomial hashing
// any prime number over a billion should suffice
internal const int _mod = (int)1e9 + 123;
// _hashBase = base (point of hashing)
// this should be a prime number larger than the number of characters used
// in my use case I am only interested in ASCII (256) characters
// for strings in languages using non-latin characters, this should be much larger
internal const long _hashBase = 257;
// _pow1 = powers of base modulo mod
internal readonly List<int> _pow1 = new List<int> { 1 };
// _pow2 = powers of base modulo 2^64
internal readonly List<long> _pow2 = new List<long> { 1L };
internal void EnsureLength(int length)
{
if (_pow1.Capacity < length)
{
_pow1.Capacity = _pow2.Capacity = length;
}
for (int currentIndx = _pow1.Count - 1; currentIndx < length; ++currentIndx)
{
_pow1.Add((int)(_pow1[currentIndx] * _hashBase % _mod));
_pow2.Add(_pow2[currentIndx] * _hashBase);
}
}
}
private class RollingHashedString
{
readonly RollingHashPowers _pows;
readonly int[] _pref1; // Hash on prefix modulo mod
readonly long[] _pref2; // Hash on prefix modulo 2^64
// Constructor from string:
internal RollingHashedString(RollingHashPowers pows, string s, bool caseInsensitive = false)
{
_pows = pows;
_pref1 = new int[s.Length + 1];
_pref2 = new long[s.Length + 1];
const long capAVal = 'A';
const long capZVal = 'Z';
const long aADif = 'a' - 'A';
unsafe
{
fixed (char* c = s)
{
// Fill arrays with polynomial hashes on prefix
for (int i = 0; i < s.Length; ++i)
{
long v = c[i];
if (caseInsensitive && capAVal <= v && v <= capZVal)
{
v += aADif;
}
_pref1[i + 1] = (int)((_pref1[i] + v * _pows._pow1[i]) % RollingHashPowers._mod);
_pref2[i + 1] = _pref2[i] + v * _pows._pow2[i];
}
}
}
}
// Rollingnomial hash of subsequence [pos, pos+len)
// If mxPow != 0, value automatically multiply on base in needed power.
// Finally base ^ mxPow
internal Tuple<int, long> Apply(int pos, int len, int mxPow = 0)
{
int hash1 = _pref1[pos + len] - _pref1[pos];
long hash2 = _pref2[pos + len] - _pref2[pos];
if (hash1 < 0)
{
hash1 += RollingHashPowers._mod;
}
if (mxPow != 0)
{
hash1 = (int)((long)hash1 * _pows._pow1[mxPow - (pos + len - 1)] % RollingHashPowers._mod);
hash2 *= _pows._pow2[mxPow - (pos + len - 1)];
}
return Tuple.Create(hash1, hash2);
}
}
private readonly RollingHashPowers _rhp;
public RollingHash(int longestLength = 0)
{
_rhp = new RollingHashPowers();
if (longestLength > 0)
{
_rhp.EnsureLength(longestLength);
}
}
public string FindCommonSubstring(string a, string b, bool caseInsensitive = false)
{
// Calculate max neede power of base:
int mxPow = Math.Max(a.Length, b.Length);
_rhp.EnsureLength(mxPow);
// Create hashing objects from strings:
RollingHashedString hash_a = new RollingHashedString(_rhp, a, caseInsensitive);
RollingHashedString hash_b = new RollingHashedString(_rhp, b, caseInsensitive);
// Binary search by length of same subsequence:
int pos = -1;
int low = 0;
int minLen = Math.Min(a.Length, b.Length);
int high = minLen + 1;
var tupleCompare = Comparer<Tuple<int, long>>.Default;
while (high - low > 1)
{
int mid = (low + high) / 2;
List<Tuple<int, long>> hashes = new List<Tuple<int, long>>(a.Length - mid + 1);
for (int i = 0; i + mid <= a.Length; ++i)
{
hashes.Add(hash_a.Apply(i, mid, mxPow));
}
hashes.Sort(tupleCompare);
int p = -1;
for (int i = 0; i + mid <= b.Length; ++i)
{
if (hashes.BinarySearch(hash_b.Apply(i, mid, mxPow), tupleCompare) >= 0)
{
p = i;
break;
}
}
if (p >= 0)
{
low = mid;
pos = p;
}
else
{
high = mid;
}
}
// Output answer:
return pos >= 0
? b.Substring(pos, low)
: string.Empty;
}
}
How to convert an integer number into its binary representation?
I'm using this code:
String input = "8";
String output = Convert.ToInt32(input, 2).ToString();
But it throws an exception:
Could not find any parsable digits
Your example has an integer expressed as a string. Let's say your integer was actually an integer, and you want to take the integer and convert it to a binary string.
int value = 8;
string binary = Convert.ToString(value, 2);
Which returns 1000.
Convert from any classic base to any base in C#
string number = "100";
int fromBase = 16;
int toBase = 10;
string result = Convert.ToString(Convert.ToInt32(number, fromBase), toBase);
// result == "256"
Supported bases are 2, 8, 10 and 16
Very Simple with no extra code, just input, conversion and output.
using System;
namespace _01.Decimal_to_Binary
{
class DecimalToBinary
{
static void Main(string[] args)
{
Console.Write("Decimal: ");
int decimalNumber = int.Parse(Console.ReadLine());
int remainder;
string result = string.Empty;
while (decimalNumber > 0)
{
remainder = decimalNumber % 2;
decimalNumber /= 2;
result = remainder.ToString() + result;
}
Console.WriteLine("Binary: {0}",result);
}
}
}
http://zamirsblog.blogspot.com/2011/10/convert-decimal-to-binary-in-c.html
public string DecimalToBinary(string data)
{
string result = string.Empty;
int rem = 0;
try
{
if (!IsNumeric(data))
error = "Invalid Value - This is not a numeric value";
else
{
int num = int.Parse(data);
while (num > 0)
{
rem = num % 2;
num = num / 2;
result = rem.ToString() + result;
}
}
}
catch (Exception ex)
{
error = ex.Message;
}
return result;
}
primitive way:
public string ToBinary(int n)
{
if (n < 2) return n.ToString();
var divisor = n / 2;
var remainder = n % 2;
return ToBinary(divisor) + remainder;
}
Another alternative but also inline solution using Enumerable and LINQ is:
int number = 25;
string binary = Enumerable.Range(0, (int)Math.Log(number, 2) + 1).Aggregate(string.Empty, (collected, bitshifts) => ((number >> bitshifts) & 1 ) + collected);
Convert.ToInt32(string, base) does not do base conversion into your base. It assumes that the string contains a valid number in the indicated base, and converts to base 10.
So you're getting an error because "8" is not a valid digit in base 2.
String str = "1111";
String Ans = Convert.ToInt32(str, 2).ToString();
Will show 15 (1111 base 2 = 15 base 10)
String str = "f000";
String Ans = Convert.ToInt32(str, 16).ToString();
Will show 61440.
static void convertToBinary(int n)
{
Stack<int> stack = new Stack<int>();
stack.Push(n);
// step 1 : Push the element on the stack
while (n > 1)
{
n = n / 2;
stack.Push(n);
}
// step 2 : Pop the element and print the value
foreach(var val in stack)
{
Console.Write(val % 2);
}
}
I know this answer would look similar to most of the answers already here, but I noticed just about none of them uses a for-loop. This code works, and can be considered simple, in the sense it will work without any special functions, like a ToString() with parameters, and is not too long as well. Maybe some prefer for-loops instead of just while-loop, this may be suitable for them.
public static string ByteConvert (int num)
{
int[] p = new int[8];
string pa = "";
for (int ii = 0; ii<= 7;ii = ii +1)
{
p[7-ii] = num%2;
num = num/2;
}
for (int ii = 0;ii <= 7; ii = ii + 1)
{
pa += p[ii].ToString();
}
return pa;
}
using System;
class Program
{
static void Main(string[] args) {
try {
int i = (int) Convert.ToInt64(args[0]);
Console.WriteLine("\n{0} converted to Binary is {1}\n", i, ToBinary(i));
} catch(Exception e) {
Console.WriteLine("\n{0}\n", e.Message);
}
}
public static string ToBinary(Int64 Decimal) {
// Declare a few variables we're going to need
Int64 BinaryHolder;
char[] BinaryArray;
string BinaryResult = "";
while (Decimal > 0) {
BinaryHolder = Decimal % 2;
BinaryResult += BinaryHolder;
Decimal = Decimal / 2;
}
BinaryArray = BinaryResult.ToCharArray();
Array.Reverse(BinaryArray);
BinaryResult = new string(BinaryArray);
return BinaryResult;
}
}
This function will convert integer to binary in C#:
public static string ToBinary(int N)
{
int d = N;
int q = -1;
int r = -1;
string binNumber = string.Empty;
while (q != 1)
{
r = d % 2;
q = d / 2;
d = q;
binNumber = r.ToString() + binNumber;
}
binNumber = q.ToString() + binNumber;
return binNumber;
}
class Program
{
static void Main(string[] args)
{
var #decimal = 42;
var binaryVal = ToBinary(#decimal, 2);
var binary = "101010";
var decimalVal = ToDecimal(binary, 2);
Console.WriteLine("Binary value of decimal {0} is '{1}'", #decimal, binaryVal);
Console.WriteLine("Decimal value of binary '{0}' is {1}", binary, decimalVal);
Console.WriteLine();
#decimal = 6;
binaryVal = ToBinary(#decimal, 3);
binary = "20";
decimalVal = ToDecimal(binary, 3);
Console.WriteLine("Base3 value of decimal {0} is '{1}'", #decimal, binaryVal);
Console.WriteLine("Decimal value of base3 '{0}' is {1}", binary, decimalVal);
Console.WriteLine();
#decimal = 47;
binaryVal = ToBinary(#decimal, 4);
binary = "233";
decimalVal = ToDecimal(binary, 4);
Console.WriteLine("Base4 value of decimal {0} is '{1}'", #decimal, binaryVal);
Console.WriteLine("Decimal value of base4 '{0}' is {1}", binary, decimalVal);
Console.WriteLine();
#decimal = 99;
binaryVal = ToBinary(#decimal, 5);
binary = "344";
decimalVal = ToDecimal(binary, 5);
Console.WriteLine("Base5 value of decimal {0} is '{1}'", #decimal, binaryVal);
Console.WriteLine("Decimal value of base5 '{0}' is {1}", binary, decimalVal);
Console.WriteLine();
Console.WriteLine("And so forth.. excluding after base 10 (decimal) though :)");
Console.WriteLine();
#decimal = 16;
binaryVal = ToBinary(#decimal, 11);
binary = "b";
decimalVal = ToDecimal(binary, 11);
Console.WriteLine("Hexidecimal value of decimal {0} is '{1}'", #decimal, binaryVal);
Console.WriteLine("Decimal value of Hexidecimal '{0}' is {1}", binary, decimalVal);
Console.WriteLine();
Console.WriteLine("Uh oh.. this aint right :( ... but let's cheat :P");
Console.WriteLine();
#decimal = 11;
binaryVal = Convert.ToString(#decimal, 16);
binary = "b";
decimalVal = Convert.ToInt32(binary, 16);
Console.WriteLine("Hexidecimal value of decimal {0} is '{1}'", #decimal, binaryVal);
Console.WriteLine("Decimal value of Hexidecimal '{0}' is {1}", binary, decimalVal);
Console.ReadLine();
}
static string ToBinary(decimal number, int #base)
{
var round = 0;
var reverseBinary = string.Empty;
while (number > 0)
{
var remainder = number % #base;
reverseBinary += remainder;
round = (int)(number / #base);
number = round;
}
var binaryArray = reverseBinary.ToCharArray();
Array.Reverse(binaryArray);
var binary = new string(binaryArray);
return binary;
}
static double ToDecimal(string binary, int #base)
{
var val = 0d;
if (!binary.All(char.IsNumber))
return 0d;
for (int i = 0; i < binary.Length; i++)
{
var #char = Convert.ToDouble(binary[i].ToString());
var pow = (binary.Length - 1) - i;
val += Math.Pow(#base, pow) * #char;
}
return val;
}
}
Learning sources:
Everything you need to know about binary
including algorithm to convert decimal to binary
class Program{
static void Main(string[] args){
try{
int i = (int)Convert.ToInt64(args[0]);
Console.WriteLine("\n{0} converted to Binary is {1}\n",i,ToBinary(i));
}catch(Exception e){
Console.WriteLine("\n{0}\n",e.Message);
}
}//end Main
public static string ToBinary(Int64 Decimal)
{
// Declare a few variables we're going to need
Int64 BinaryHolder;
char[] BinaryArray;
string BinaryResult = "";
while (Decimal > 0)
{
BinaryHolder = Decimal % 2;
BinaryResult += BinaryHolder;
Decimal = Decimal / 2;
}
// The algoritm gives us the binary number in reverse order (mirrored)
// We store it in an array so that we can reverse it back to normal
BinaryArray = BinaryResult.ToCharArray();
Array.Reverse(BinaryArray);
BinaryResult = new string(BinaryArray);
return BinaryResult;
}
}//end class Program
BCL provided Convert.ToString(n, 2) is good, but in case you need an alternate implementation which is few ticks faster than BCL provided one.
Following custom implementation works for all integers(-ve and +ve).
Original source taken from https://davidsekar.com/algorithms/csharp-program-to-convert-decimal-to-binary
static string ToBinary(int n)
{
int j = 0;
char[] output = new char[32];
if (n == 0)
output[j++] = '0';
else
{
int checkBit = 1 << 30;
bool skipInitialZeros = true;
// Check the sign bit separately, as 1<<31 will cause
// +ve integer overflow
if ((n & int.MinValue) == int.MinValue)
{
output[j++] = '1';
skipInitialZeros = false;
}
for (int i = 0; i < 31; i++, checkBit >>= 1)
{
if ((n & checkBit) == 0)
{
if (skipInitialZeros)
continue;
else
output[j++] = '0';
}
else
{
skipInitialZeros = false;
output[j++] = '1';
}
}
}
return new string(output, 0, j);
}
Above code is my implementation. So, I'm eager to hear any feedback :)
// I use this function
public static string ToBinary(long number)
{
string digit = Convert.ToString(number % 2);
if (number >= 2)
{
long remaining = number / 2;
string remainingString = ToBinary(remaining);
return remainingString + digit;
}
return digit;
}
static void Main(string[] args)
{
Console.WriteLine("Enter number for converting to binary numerical system!");
int num = Convert.ToInt32(Console.ReadLine());
int[] arr = new int[16];
//for positive integers
if (num > 0)
{
for (int i = 0; i < 16; i++)
{
if (num > 0)
{
if ((num % 2) == 0)
{
num = num / 2;
arr[16 - (i + 1)] = 0;
}
else if ((num % 2) != 0)
{
num = num / 2;
arr[16 - (i + 1)] = 1;
}
}
}
for (int y = 0; y < 16; y++)
{
Console.Write(arr[y]);
}
Console.ReadLine();
}
//for negative integers
else if (num < 0)
{
num = (num + 1) * -1;
for (int i = 0; i < 16; i++)
{
if (num > 0)
{
if ((num % 2) == 0)
{
num = num / 2;
arr[16 - (i + 1)] = 0;
}
else if ((num % 2) != 0)
{
num = num / 2;
arr[16 - (i + 1)] = 1;
}
}
}
for (int y = 0; y < 16; y++)
{
if (arr[y] != 0)
{
arr[y] = 0;
}
else
{
arr[y] = 1;
}
Console.Write(arr[y]);
}
Console.ReadLine();
}
}
This might be helpful if you want a concise function that you can call from your main method, inside your class. You may still need to call int.Parse(toBinary(someint)) if you require a number instead of a string but I find this method work pretty well. Additionally, this can be adjusted to use a for loop instead of a do-while if you'd prefer.
public static string toBinary(int base10)
{
string binary = "";
do {
binary = (base10 % 2) + binary;
base10 /= 2;
}
while (base10 > 0);
return binary;
}
toBinary(10) returns the string "1010".
I came across this problem in a coding challenge where you have to convert 32 digit decimal to binary and find the possible combination of the substring.
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Numerics;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApp2
{
class Program
{
public static void Main()
{
int numberofinputs = int.Parse(Console.ReadLine());
List<BigInteger> inputdecimal = new List<BigInteger>();
List<string> outputBinary = new List<string>();
for (int i = 0; i < numberofinputs; i++)
{
inputdecimal.Add(BigInteger.Parse(Console.ReadLine(), CultureInfo.InvariantCulture));
}
//processing begins
foreach (var n in inputdecimal)
{
string binary = (binaryconveter(n));
subString(binary, binary.Length);
}
foreach (var item in outputBinary)
{
Console.WriteLine(item);
}
string binaryconveter(BigInteger n)
{
int i;
StringBuilder output = new StringBuilder();
for (i = 0; n > 0; i++)
{
output = output.Append(n % 2);
n = n / 2;
}
return output.ToString();
}
void subString(string str, int n)
{
int zeroodds = 0;
int oneodds = 0;
for (int len = 1; len <= n; len++)
{
for (int i = 0; i <= n - len; i++)
{
int j = i + len - 1;
string substring = "";
for (int k = i; k <= j; k++)
{
substring = String.Concat(substring, str[k]);
}
var resultofstringanalysis = stringanalysis(substring);
if (resultofstringanalysis.Equals("both are odd"))
{
++zeroodds;
++oneodds;
}
else if (resultofstringanalysis.Equals("zeroes are odd"))
{
++zeroodds;
}
else if (resultofstringanalysis.Equals("ones are odd"))
{
++oneodds;
}
}
}
string outputtest = String.Concat(zeroodds.ToString(), ' ', oneodds.ToString());
outputBinary.Add(outputtest);
}
string stringanalysis(string str)
{
int n = str.Length;
int nofZeros = 0;
int nofOnes = 0;
for (int i = 0; i < n; i++)
{
if (str[i] == '0')
{
++nofZeros;
}
if (str[i] == '1')
{
++nofOnes;
}
}
if ((nofZeros != 0 && nofZeros % 2 != 0) && (nofOnes != 0 && nofOnes % 2 != 0))
{
return "both are odd";
}
else if (nofZeros != 0 && nofZeros % 2 != 0)
{
return "zeroes are odd";
}
else if (nofOnes != 0 && nofOnes % 2 != 0)
{
return "ones are odd";
}
else
{
return "nothing";
}
}
Console.ReadKey();
}
}
}
int x=550;
string s=" ";
string y=" ";
while (x>0)
{
s += x%2;
x=x/2;
}
Console.WriteLine(Reverse(s));
}
public static string Reverse( string s )
{
char[] charArray = s.ToCharArray();
Array.Reverse( charArray );
return new string( charArray );
}
This was a interesting read i was looking for a quick copy paste.
I knew i had done this before long ago with bitmath differently.
Here was my take on it.
// i had this as a extension method in a static class (this int inValue);
public static string ToBinaryString(int inValue)
{
string result = "";
for (int bitIndexToTest = 0; bitIndexToTest < 32; bitIndexToTest++)
result += ((inValue & (1 << (bitIndexToTest))) > 0) ? '1' : '0';
return result;
}
You could stick spacing in there with a bit of modulos in the loop.
// little bit of spacing
if (((bitIndexToTest + 1) % spaceEvery) == 0)
result += ' ';
You could probably use or pass in a stringbuilder and append or index directly to avoid deallocations and also get around the use of += this way;
var b = Convert.ToString(i,2).PadLeft(32,'0').ToCharArray().Reverse().ToArray();
Just one line for 8 bit
Console.WriteLine(Convert.ToString(n, 2).PadLeft(8, '0'));
where n is the number
So, bitfields. Specifically, large bitfields. I understand how to manipulate individual values in a bitfield, but how would I go about doing this on a large set, such as say:
uint[] bitfield = new uint[4] { 0x0080000, 0x00FA3020, 0x00C8000, 0x0FF00D0 };
The specific problem I'm having is doing left and right shifts that carry through across the whole array. So for instance, if I did a >> 4 on the above array, I'd end up with:
uint[4] { 0x0008000, 0x000FA302, 0x000C800, 0x00FF00D };
Now, an (overly) simplistic algorithm here might look something like (this is me writting code on the fly):
int shift = 4;
for (int i = 0; i <= shift; i++) {
for (int j = bitfield.GetUpperBound(0); j > 0; j--) {
bitfield[j] = bitfield[j] >> 1;
bitfield[j] = bitfield[j] + ((bitfield[j-1] & 1) << (sizeof(uint)*8));
}
bitfield[0] = bitfield[0] >> 1;
}
Is there anything built in that might ease working with this sort of data?
What makes you think that BitArray uses bools internally? It uses Boolean values to represent the bits in terms of the API, but under the hood I believe it uses an int[].
I'm not sure if it's the best way to do it, but this could work (constraining shifts to be in the range 0-31.
public static void ShiftLeft(uint[] bitfield, int shift) {
if(shift < 0 || shift > 31) {
// handle error here
return;
}
int len = bitfield.Length;
int i = len - 1;
uint prev = 0;
while(i >= 0) {
uint tmp = bitfield[i];
bitfield[i] = bitfield[i] << shift;
if(i < len - 1) {
bitfield[i] |= (uint)(prev & (1 >> shift) - 1 ) >> (32 - shift);
}
prev = tmp;
i--;
}
}
public static void ShiftRight(uint[] bitfield, int shift) {
if(shift < 0 || shift > 31) {
// handle error here
return;
}
int len = bitfield.Length;
int i = 0;
uint prev = 0;
while(i < len) {
uint tmp = bitfield[i];
bitfield[i] = bitfield[i] >> shift;
if(i > 0) {
bitfield[i] |= (uint)(prev & (1 << shift) - 1 ) << (32 - shift);
}
prev = tmp;
i++;
}
}
PD: With this change, you should be able to handle shifts greater than 31 bits. Could be refactored to make it look a little less ugly, but in my tests, it works and it doesn't seem too bad performance-wise (unless, there's actually something built in to handle large bitsets, which could be the case).
public static void ShiftLeft(uint[] bitfield, int shift) {
if(shift < 0) {
// error
return;
}
int intsShift = shift >> 5;
if(intsShift > 0) {
if(intsShift > bitfield.Length) {
// error
return;
}
for(int j=0;j < bitfield.Length;j++) {
if(j > intsShift + 1) {
bitfield[j] = 0;
} else {
bitfield[j] = bitfield[j+intsShift];
}
}
BitSetUtils.ShiftLeft(bitfield,shift - intsShift * 32);
return;
}
int len = bitfield.Length;
int i = len - 1;
uint prev = 0;
while(i >= 0) {
uint tmp = bitfield[i];
bitfield[i] = bitfield[i] << shift;
if(i < len - 1) {
bitfield[i] |= (uint)(prev & (1 >> shift) - 1 ) >> (32 - shift);
}
prev = tmp;
i--;
}
}
public static void ShiftRight(uint[] bitfield, int shift) {
if(shift < 0) {
// error
return;
}
int intsShift = shift >> 5;
if(intsShift > 0) {
if(intsShift > bitfield.Length) {
// error
return;
}
for(int j=bitfield.Length-1;j >= 0;j--) {
if(j >= intsShift) {
bitfield[j] = bitfield[j-intsShift];
} else {
bitfield[j] = 0;
}
}
BitSetUtils.ShiftRight(bitfield,shift - intsShift * 32);
return;
}
int len = bitfield.Length;
int i = 0;
uint prev = 0;
while(i < len) {
uint tmp = bitfield[i];
bitfield[i] = bitfield[i] >> shift;
if(i > 0) {
bitfield[i] |= (uint)(prev & (1 << shift) - 1 ) << (32 - shift);
}
prev = tmp;
i++;
}
}
Using extension methods, you could do this:
public static class BitArrayExtensions
{
public static void DownShift(this BitArray bitArray, int places)
{
for (var i = 0; i < bitArray.Length; i++)
{
bitArray[i] = i + places < bitArray.Length && bitArray[i + places];
}
}
public static void UpShift(this BitArray bitArray, int places)
{
for (var i = bitArray.Length - 1; i >= 0; i--)
{
bitArray[i] = i - places >= 0 && bitArray[i - places];
}
}
}
Unfortunately, I couldn't come up with a way to overload the shift operators. (Mainly because BitArray is sealed.)
If you intend to manipulate ints or uints, you could create extension methods for inserting bits into / extracting bits from the BitArray. (BitArray has a constructor that takes an array of ints, but that only takes you that far.)
This doesn't cover specifically shifting, but could be useful for working with large sets. It's in C, but I think it could be easily adapted to C#
Is there a practical limit to the size of bit masks?