longest-common-subsequence.java

public class LongestCommonSubsequence { 
  
    /* Returns length of LCS for X[0..m-1], Y[0..n-1] */
    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] = max(L[i - 1][j], L[i][j - 1]); 
            } 
        } 
        return L[m][n]; 
    } 
  
    /* Utility function to get max of 2 integers */
    int max(int a, int b) 
    { 
        return (a > b) ? a : b; 
    }