Longest Common Sub Sequence between two string - Java Algorithm

Java examples for Algorithm:String

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Description

Longest Common Sub Sequence between two string

Demo Code


public class Main {

  public static void main(String[] args) {

    String str1 = "aaav";
    String str2 = "aaad";

    int len1 = str1.length();
    int len2 = str2.length();

    int[][] cache = new int[len1 + 1][len2 + 1];
    int[][] direction = new int[len1 + 1][len2 + 1];

    for (int i = 1; i <= len1; i++) {
      for (int j = 1; j <= len2; j++) {
        if (str1.charAt(i - 1) == str2.charAt(j - 1)) {
          cache[i][j] = cache[i - 1][j - 1] + 1;
          direction[i][j] = 1;/*from w ww . j a va2  s . c  om*/
        } else if (cache[i - 1][j] >= cache[i][j - 1]) {
          cache[i][j] = cache[i - 1][j];
          direction[i][j] = 2;
        } else {
          cache[i][j] = cache[i][j - 1];
          direction[i][j] = 3;
        }
      }
    }

    String longestCommonSubseq = "";
    int i = len1;
    int j = len2;
    while (i != 0 && j != 0) {
      if (direction[i][j] == 1) {
        longestCommonSubseq = str1.charAt(i - 1) + longestCommonSubseq;
        i = i - 1;
        j = j - 1;
      }
      if (direction[i][j] == 2) {
        i = i - 1;
      }
      if (direction[i][j] == 3) {
        j = j - 1;
      }
    }

    System.out.println("Str1: " + str1);
    System.out.println("Str2: " + str2);
    System.out.println("LCS is: " + longestCommonSubseq);

  }

}

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