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Count Matching Subsequences

This is what I need to do:
Create a function that receives a text string, and a search string, and returns how many times the search string appears in the string, as a subsequence of its letters in order.
For example, if you receive the word "Hhoola" and the substring "hola", the answer would be 4, because you could take the first H with the first O (and with the L and with the A), the first H with the second O, the second H with the first O, or the second H with the second O. If you receive "hobla", the answer would be 1. If you receive "ohla", the answer would be 0, because after the H there is no O to complete the sequence in order.
This is what i got so far:
int count = 0;
void Function(string text, string subText)
{
for (int i = 0; i < text.Length; i++)
{
if (text[i] == subText[0])
{
for (int j = 0; j < subText.Length; j++)
{
if (text[i + j] != subText[j])
{
break;
}
if (j == subText.Length - 1)
{
count++;
}
}
}
}
}
string text = Console.ReadLine().ToLower();
string subText = Console.ReadLine().ToLower();
ReceibeText(text, subText);

The code should look like this. Code doesn't work but is close.
public class SubSequences
{
string input = "";
string word = "";
int count = 0;
public void FindMatches(string input, string word)
{
this.input = input;
this.word = word;
FindMatchesRecursive(0, 0);
}
public void FindMatchesRecursive(int inputIndex, int wordIndex)
{
for (int i = inputIndex; i < input.Length - word.Length; i++ )
{
for (int j = wordIndex; j < input.Length - word.Length; j++)
{
if (word.Substring(i) == input.Substring(j))
{
if (j == word.Length)
{
FindMatchesRecursive(i + 1, j + 1);
}
else
{
Console.WriteLine("Word Matches");
}
}
}
}
}

Trouble creating algorithm that modifies elements of a 2d array

I am having trouble editing the values of a 2d char array.
char[,] chrRaster = new char[4, 5];
After adding values to the array and printing it to the console, I get:
// Input example:
*****
**.**
*****
****.
I am trying to make an algorithm that replaces every '*' that is beside, under or above a '.' by a '.' and then printing this to the console.
// Output after algorithm example:
**.**
*...*
**.*.
***..
I have tried converting the 2d char array to a 2d string array and then using IndexOf('*') to replace every '*' that is beside, under or above a '.', and I also tried calculating this using a number of if and for loops without any luck.
static void Main(string[] args)
{
// Variablen
int intTestgeval = 0; // Number of times you want program to repeat
int intN = 0; // Number of rows
int intM = 0; // Number of coloms
char chrGrond; // Used to store '*' or '.'
char[,] chrRaster; // 2d char array used to store all values
// Code
try
{
intTestgeval = Int32.Parse(Console.ReadLine()); // Number of times program will repeat
if(intTestgeval > 150) // Program can not repeat more then 150 times
{
throw new Exception();
}
}
catch (Exception)
{
Environment.Exit(0);
}
intN = Controle(intN); // Number of rows ophalen
intM = Controle(intM); // Number of Coloms ophalen
chrRaster = new char[intN, intM]; // Initializing array with user input
for (int intR = 0; intR < intTestgeval; intR++) // Print 2d array to console
{
for(int intY = 0; intY < intN; intY++)
{
for(int intZ = 0; intZ < intM; intZ++)
{
chrGrond = Convert.ToChar(Console.ReadKey().KeyChar);
chrRaster[intY, intZ] = chrGrond;
}
Console.WriteLine();
}
instorten[intR] = Instorten(chrRaster, intN, intM); // Ignore this part, that's another part of my assignment not related to my question.
}
}
static int Controle( int intX )
{
try
{
intX = Int32.Parse(Console.ReadLine());
if (intX > 150 || intX < 1) // Length of row and colom can not exceed 20 and can not go lower then 1
{
throw new Exception();
}
return intX;
}
catch // Program will off if value does not meet requirements
{
Environment.Exit(0);
return intX;
}
}
// It is this part of the program I need help with. This is what I tried but can't get any further
static int Instorten(char[,] chrRaster, int intN, int intM)
{
for (int intY = 0; intY < intN; intY++)
{
for (int intZ = 0; intZ < intM; intZ++)
{
if(chrRaster[intY, intZ] == '.' && chrRaster[intY, intZ + 1] == '*' || chrRaster[intY, intZ] == '*' && chrRaster[intY, intZ + 1] == '.')
{
}
}
Console.WriteLine();
}
int intm = 0;
return intm;
}
}

One way to do this would be to make a copy of the array and then iterate over it, examining each item. If the item is a '.', then update the neighbors of this item in the original array.
To determine the neighbors, we simply add one to the row to get the neighbor below, subtract one from the row to get the neighbor above, and similarly we can get the right and left neighbors by adding/subtracting from the column value. Of course we need to ensure that we're inside the bounds of the array before doing anything.
We could write a method with this logic that might look like:
private static void ExposeDotNeighbors(char[,] input)
{
if (input == null) return;
// Make a copy of the input array that we can iterate over
// so that we don't analyze items that we've already changed
var copy = (char[,]) input.Clone();
for (var row = 0; row <= copy.GetUpperBound(0); row++)
{
for (var col = 0; col <= copy.GetUpperBound(1); col++)
{
if (copy[row, col] == '.')
{
// Update neighbors in original array
// Above = [row - 1, col], Below = [row + 1, col],
// Left = [row, col - 1], Right = [row, col + 1]
// Before updating, make sure we're inside the array bounds
if (row > 0) input[row - 1, col] = '.';
if (row < input.GetUpperBound(0)) input[row + 1, col] = '.';
if (col > 0) input[row, col - 1] = '.';
if (col < input.GetUpperBound(1)) input[row, col + 1] = '.';
}
}
}
}
We can also write some helper methods that will give us the initial array and to print an array to the console (also one that will write a header to the console):
private static char[,] GetInitialArray()
{
var initialArray = new char[4, 5];
for (var row = 0; row <= initialArray.GetUpperBound(0); row++)
{
for (var col = 0; col <= initialArray.GetUpperBound(1); col++)
{
if ((row == 1 && col == 2) || (row == 3 && col == 4))
{
initialArray[row, col] = '.';
}
else
{
initialArray[row, col] = '*';
}
}
}
return initialArray;
}
private static void PrintArrayToConsole(char[,] input)
{
if (input == null) return;
for (var row = 0; row <= input.GetUpperBound(0); row++)
{
for (var col = 0; col <= input.GetUpperBound(1); col++)
{
Console.Write(input[row, col]);
}
Console.WriteLine();
}
}
private static void WriteHeader(string headerText)
{
if (string.IsNullOrEmpty(headerText))
{
Console.Write(new string('═', Console.WindowWidth));
return;
}
Console.WriteLine('╔' + new string('═', headerText.Length + 2) + '╗');
Console.WriteLine($"║ {headerText} ║");
Console.WriteLine('╚' + new string('═', headerText.Length + 2) + '╝');
}
With these helper methods, we can then write code like:
private static void Main()
{
var chrRaster = GetInitialArray();
WriteHeader("Before");
PrintArrayToConsole(chrRaster);
ExposeDotNeighbors(chrRaster);
WriteHeader("After");
PrintArrayToConsole(chrRaster);
GetKeyFromUser("\nDone! Press any key to exit...");
}
And out output would look like:
I noticed that you also appear to be getting the values from the user, and using try/catch blocks to validate the input. A better approach might be to write a helper method that takes in a string that represents the "prompt" to the user, and a validation method that can be used to validate the input. With this, we can keep asking the user for input until they enter something valid.
Below are methods that get an integer and a character from the user, and allow the caller to pass in a function that can be used for validation. These methods will not return until the user enters valid input:
private static char GetCharFromUser(string prompt, Func<char, bool> validator = null)
{
char result;
var cursorTop = Console.CursorTop;
do
{
ClearSpecificLineAndWrite(cursorTop, prompt);
result = Console.ReadKey().KeyChar;
} while (!(validator?.Invoke(result) ?? true));
Console.WriteLine();
return result;
}
private static int GetIntFromUser(string prompt, Func<int, bool> validator = null)
{
int result;
var cursorTop = Console.CursorTop;
do
{
ClearSpecificLineAndWrite(cursorTop, prompt);
} while (!int.TryParse(Console.ReadLine(), out result) ||
!(validator?.Invoke(result) ?? true));
return result;
}
private static void ClearSpecificLineAndWrite(int cursorTop, string message)
{
Console.SetCursorPosition(0, cursorTop);
Console.Write(new string(' ', Console.WindowWidth));
Console.SetCursorPosition(0, cursorTop);
Console.Write(message);
}
We can then re-write our GetInitialArray method to use these methods to get the dimensions and values from the user:
private static char[,] GetInitialArray()
{
const int maxCols = 20;
const int maxRows = 20;
var numCols = GetIntFromUser(
$"How many columns do you want (1 - {maxCols}): ",
i => i > 0 && i <= maxCols);
var numRows = GetIntFromUser(
$"How many rows do you want (1 - {maxRows}): ",
i => i > 0 && i <= maxRows);
var initialArray = new char[numRows, numCols];
for (var row = 0; row <= initialArray.GetUpperBound(0); row++)
{
for (var col = 0; col <= initialArray.GetUpperBound(1); col++)
{
initialArray[row, col] = GetCharFromUser(
$"Enter value for [{row}, {col}] ('.' or '*'): ",
c => c == '.' || c == '*');
}
}
return initialArray;
}
And now our output might look like this:
If you try it, notice that you cannot enter an illegal value. The program just waits for you to read the instructions and enter a valid number or character. :)

Here is the algorithm that does what you want. I have tried to explain my code in the comments. The output will match what you're looking for.
static void Main(string[] args)
{
char STAR = '*';
char DOT = '.';
var input = new char[,]
{
{ STAR,STAR,STAR,STAR,STAR},
{ STAR,STAR,DOT,STAR,STAR},
{ STAR,STAR,STAR,STAR,STAR},
{ STAR,STAR,STAR,STAR,DOT}
};
var output = new char[4, 5];
// Copy each from input to output, checking if it touches a '.'
for (int x = 0; x < 4; x++)
{
for (int y = 0; y < 5; y ++)
{
if (input[x, y] == STAR)
{
var isDot = false;
// Check left
if (x > 0)
isDot = input[x - 1, y] == DOT;
// Check right
if (x < 3)
isDot = isDot || (input[x + 1, y] == DOT);
// Check above
if (y > 0)
isDot = isDot || (input[x, y - 1] == DOT);
// Check below
if (y < 4)
isDot = isDot || (input[x, y + 1]) == DOT;
output[x, y] = isDot ? DOT : STAR;
}
else
{
output[x, y] = input[x, y];
}
}
}
// Print output
for (int x = 0; x < 4; x ++)
{
for (int y = 0; y < 5; y ++)
{
Console.Write(output[x, y]);
}
Console.WriteLine();
}
Console.Read();
}

You can go like this :
using System;
public class chars
{
public static void Main(string[] args)
{
char[,] charArray = new char[,] {{'*','*','*','*','*'},
{'*','*','.','*','*'},
{'*','*','*','*','*'},
{'*','*','*','*','.'}};
int[,] holdIndex = new int[4, 5];
for(int i = 0; i<4; i++) // get allindexes containing '.'
{
for(int j = 0; j<5; j++)
{
if(charArray[i,j] == '.')
holdIndex[i,j] = 1;
else
holdIndex[i,j] = 0;
}
}
for(int i = 0; i<4; i++)
{
for(int j = 0; j<5; j++)
{
if(holdIndex[i,j] == 1)
{
if(i!=0)
charArray[i-1,j] = '.'; //up
if(j!=0)
charArray[i,j-1] = '.'; // left
if(j!=4)
charArray[i,j+1] = '.'; //right
if(i!=3)
charArray[i+1,j] = '.'; //down
}
}
}
for(int i = 0; i<4; i++)
{
for(int j = 0; j<5; j++)
{
Console.Write(charArray[i,j]);
}
Console.WriteLine();
}
Console.Read();
}
}

Sequence of marching chars in 2 strings

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 ) );
}
}

Count Number of Changes Comparing two string in c# [closed]

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I want to find out Number of changes comparing two string.
Example:
String 1:
I hope to do something good from this chance.I think my Test form will
help me in ODI. Scoring runs in international cricket, regardless of
the format, gives a player confidence.
string 2:
"I hope to do something good this chance. I think my Testing form will
help me in ODI Format. Scoring runs in latest international cricket,
regardless of the format, gives a playing confidence."
Expected Output: 5.(ignoring space & newline)
Changes are:
from(delete from string 2),
Testing(modified in string 2),
Format(extra addition in string 2),
latest(extra addition in string 2),
playing(modified in string 2).
Have any algorithm for count the number of changes?

You problem is quite similar to comparing two files.. Difference is In file comparison files are compared by comparing text in a single line. In your case it white space would be a separator instead of Newline.
Typically this is accomplished by finding the Longest Common Subsequence. Here is a related document which explains it: https://nanohub.org/infrastructure/rappture/export/2719/trunk/gui/src/diff.pdf
For finding LCS:
public static int GetLCS(string str1, string str2)
{
int[,] table;
return GetLCSInternal(str1, str2, out table);
}
private static int GetLCSInternal(string str1, string str2, out int[,] matrix)
{
matrix = null;
if (string.IsNullOrEmpty(str1) || string.IsNullOrEmpty(str2))
{
return 0;
}
int[,] table = new int[str1.Length + 1, str2.Length + 1];
for (int i = 0; i < table.GetLength(0); i++)
{
table[i, 0] = 0;
}
for(int j= 0;j<table.GetLength(1); j++)
{
table[0,j] = 0;
}
for (int i = 1; i < table.GetLength(0); i++)
{
for (int j = 1; j < table.GetLength(1); j++)
{
if (str1[i-1] == str2[j-1])
table[i, j] = table[i - 1, j - 1] + 1;
else
{
if (table[i, j - 1] > table[i - 1, j])
table[i, j] = table[i, j - 1];
else
table[i, j] = table[i - 1, j];
}
}
}
matrix = table;
return table[str1.Length, str2.Length];
}
//Reading Out All LCS sorted in lexicographic order
using System;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using System.Text;
namespace LambdaPractice
{
class Program
{
static int[,] c;
static int max(int a, int b)
{
return (a > b) ? a : b;
}
static int LCS(string s1, string s2)
{
for (int i = 1; i <= s1.Length; i++)
c[i,0] = 0;
for (int i = 1; i <= s2.Length; i++)
c[0, i] = 0;
for (int i=1;i<=s1.Length;i++)
for (int j = 1; j <= s2.Length; j++)
{
if (s1[i-1] == s2[j-1])
c[i, j] = c[i - 1, j - 1] + 1;
else
{
c[i, j] = max(c[i - 1, j], c[i, j - 1]);
}
}
return c[s1.Length, s2.Length];
}
/* Prints one LCS
static string BackTrack(string s1, string s2, int i, int j)
{
if (i == 0 || j == 0)
return "";
if (s1[i - 1] == s2[j - 1])
return BackTrack(s1, s2, i - 1, j - 1) + s1[i - 1];
else if (c[i - 1, j] > c[i, j - 1])
return BackTrack(s1, s2, i - 1, j);
else
return BackTrack(s1, s2, i, j - 1);
}*/
static SortedSet<string> backtrack(string s1, string s2, int i, int j)
{
if (i == 0 || j == 0)
return new SortedSet<string>(){""} ;
else if (s1[i - 1] == s2[j - 1])
{
SortedSet<string> temp = new SortedSet<string>();
SortedSet<string> holder = backtrack(s1, s2, i - 1, j - 1);
if (holder.Count == 0)
{
temp.Add(s1[i - 1]);
}
foreach (string str in holder)
temp.Add(str + s1[i - 1]);
return temp;
}
else
{
SortedSet<string> Result = new SortedSet<string>() ;
if (c[i - 1, j] >= c[i, j - 1])
{
SortedSet<string> holder = backtrack(s1, s2, i - 1, j);
foreach (string s in holder)
Result.Add(s);
}
if (c[i, j - 1] >= c[i - 1, j])
{
SortedSet<string> holder = backtrack(s1, s2, i, j - 1);
foreach (string s in holder)
Result.Add(s);
}
return Result;
}
}
static void Main(string[] args)
{
string s1, s2;
s1 = Console.ReadLine();
s2 = Console.ReadLine();
c = new int[s1.Length+1, s2.Length+1];
LCS(s1, s2);
// Console.WriteLine(BackTrack(s1, s2, s1.Length, s2.Length));
// Console.WriteLine(s1.Length);
SortedSet<string> st = backtrack(s1, s2, s1.Length, s2.Length);
foreach (string str in st)
Console.WriteLine(str);
GC.Collect();
Console.ReadLine();
}
}
}

could you check this might be useful somehow, I would say you'll use a lot of control statements (if/else or switch) for result sets.

You can do it relatively easy, if you you consider a string as modified if it is starting with another string:
void Main()
{
var a = "I hope to do something good from this chance.I think my Test form will help me in ODI.Scoring runs in international cricket, regardless of the format, gives a player confidence.";
var b = "I hope to do something good this chance. I think my Testing form will help me in ODI Format. Scoring runs in latest international cricket, regardless of the format, gives a playing confidence.";
var d = new Difference(a,b);
Console.WriteLine("Number of differences: {0}", d.Count);
foreach (var diff in d.Differences)
{
Console.WriteLine("Different: {0}", diff);
}
}
class Difference
{
string a;
string b;
List<string> notInA;
List<string> notInB;
public int Count
{
get { return notInA.Count + notInB.Count; }
}
public IEnumerable<string> Differences
{
get { return notInA.Concat(notInB); }
}
public Difference(string a, string b)
{
this.a = a;
this.b = b;
var itemsA = Split(a);
var itemsB = Split(b);
var changedPairs =
from x in itemsA
from y in itemsB
where (x.StartsWith(y) || y.StartsWith(x)) && y != x
select new { x, y };
var softChanged = changedPairs.SelectMany(p => new[] {p.x, p.y}).Distinct().ToList();
notInA = itemsA.Except(itemsB).Except(softChanged).ToList();
notInB = itemsB.Except(itemsA).Except(softChanged).ToList();
}
IEnumerable<string> Split(string x)
{
return x.Split(new[] { " ", ".", ","}, StringSplitOptions.RemoveEmptyEntries);
}
}
Output:
Number of differences: 5
Different: from
Different: player
Different: Format
Different: latest
Different: playing

Longest Common Subsequence

Hi this is my code for longest common subsequence for 2 strings in c# . I need help in backtracking . I need to find out the subsequence : GTCGT
String str1 = "GTCGTTCG";
String str2 = "ACCGGTCGAGTG";
int[,] l = new int[str1.Length, str2.Length]; // String 1 length and string 2 length storing it in a 2-dimensional array
int lcs = -1;
string substr = string.Empty;
int end = -1;
for (int i = 0; i <str1.Length ; i++) // Looping based on string1 length
{
for (int j = 0; j < str2.Length; j++) // Looping based on string2 Length
{
if (str1[i] == str2[j]) // if match found
{
if (i == 0 || j == 0) // i is first element or j is first elemnt then array [i,j] = 1
{
l[i, j] = 1;
}
else
{
l[i, j] = l[i - 1, j - 1] + 1; // fetch the upper value and increment by 1
}
if (l[i, j] > lcs)
{
lcs = l[i, j]; // store lcs value - how many time lcs is found
end = i; // index on longest continuous string
}
}
else // if match not found store zero initialze the array value by zero
{
l[i, j] = 0;
}
}

Your function needs to return a collection of strings. There might be several longest common sub-sequence with same length.
public List<string> LCS(string firstString, string secondString)
{
// to create the lcs table easier which has first row and column empty.
string firstStringTemp = " " + firstString;
string secondStringTemp = " " + secondString;
// create the table
List<string>[,] temp = new List<string>[firstStringTemp.Length, secondStringTemp.Length];
// loop over all items in the table.
for (int i = 0; i < firstStringTemp.Length; i++)
{
for (int j = 0; j < secondStringTemp.Length; j++)
{
temp[i, j] = new List<string>();
if (i == 0 || j == 0) continue;
if (firstStringTemp[i] == secondStringTemp[j])
{
var a = firstStringTemp[i].ToString();
if (temp[i - 1, j - 1].Count == 0)
{
temp[i, j].Add(a);
}
else
{
foreach (string s in temp[i - 1, j - 1])
{
temp[i, j].Add(s + a);
}
}
}
else
{
List<string> b = temp[i - 1, j].Concat(temp[i, j - 1]).Distinct().ToList();
if (b.Count == 0) continue;
int max = b.Max(p => p.Length);
b = b.Where(p => p.Length == max).ToList();
temp[i, j] = b;
}
}
}
return temp[firstStringTemp.Length - 1, secondStringTemp.Length - 1];
}
You need to have a collection set in each entry of table. So you can still keep different strings with the same length in each cell of table.

As far as I've understood your question, I think you want to know the subsequence value i.e. that string. So, to get the subsequence, I've learnt a little bit differently. First, I calculate the table the one we do in standard Longest Common Subsequence (LCS) problem. Then I traverse the table to get the subsequence value. Sorry, I'm not familiar with C#, so, I will give you CPP code. Please have a look and let me know if you face any problem.
#include<iostream>
#include<vector>
#include<string>
using namespace std;
string printLongestCommonSubsequence(vector<vector<int> >& dp, int m, int n, string text1, string text2){
int i = m, j = n;
string lcs = "";
while(i > 0 && j > 0){
if(text1[i-1] == text2[j-1]){
lcs.push_back(text1[i-1]);
i--; j--;
}
else{
if(dp[i][j-1] > dp[i-1][j]) j--;
else i--;
}
}
reverse(lcs.begin(), lcs.end());
return lcs;
}
string longestCommonSubsequence(string text1, string text2){
int m = text1.size();
int n = text2.size();
vector<vector<int> > dp(m+1, vector<int>(n+1));
//initialization
for(int i=0; i<m+1; i++){
for(int j=0; j<n+1; j++){
if(i == 0 || j == 0) dp[i][j] = 0;
}
}
//solving the subproblems to solve the bigger problems
for(int i=1; i<m+1; i++){
for(int j=1; j<n+1; j++){
if(text1[i-1] == text2[j-1])
dp[i][j] = 1 + dp[i-1][j-1];
else
dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
}
}
return printLongestCommonSubsequence(dp, m, n, text1, text2);
}
int main(){
string text1, text2;
cout<<"Enter the first string: ";
cin>>text1;
cout<<"\nEnter the second string: ";
cin>>text2;
string lcs = longestCommonSubsequence(text1, text2);
cout<<"Longest Common Subsequence is: "<<lcs<<endl;
return(0);
}
Please have a look at the diagram.
With respect to printing the LCS,
The basic idea is:
When the characters are equal of both the strings then move towards diagonal.
When the characters are not equal of both the strings then move towards the maximum of both the directions.
I hope this helps 🙂
Happy Learning
Thanks