LongestCommonSubsequence.c

// Find out the Longest Common Subsequence of two given strings.Calculate length of the LCS.

#include <stdio.h>
#include <string.h>

void LCS(char *X, char *Y, int m, int n)
{
    int L[m + 1][n + 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] = (L[i - 1][j] > L[i][j - 1]) ? L[i - 1][j] : L[i][j - 1];
        }
    }

    int index = L[m][n];

    char lcs[index + 1];
    lcs[index] = '\0'; 

    int i = m, j = n;
    while (i > 0 && j > 0)
    {
        if (X[i - 1] == Y[j - 1])
        {
            lcs[index - 1] = X[i - 1];
            i--;
            j--;
            index--;
        }
        else if (L[i - 1][j] > L[i][j - 1])
            i--;
        else
            j--;
    }

    printf("LCS: %s\n", lcs);
    printf("LCS Length: %d\n", L[m][n]);
}

int main()
{
    char X[100], Y[100];

    printf("Enter the first string: ");
    scanf("%s", X);
    printf("Enter the second string: ");
    scanf("%s", Y);

    int m = strlen(X);
    int n = strlen(Y);

    LCS(X, Y, m, n);

    return 0;
}