Print Longest Common Subsequence
This program prints the longest common subsequence between two strings.
Problem Statement
Write a Java program to print longest common subsequence of "Eduinq" and "Enquiry".
Source Code
| 1 | public class PrintLCS { |
| 2 | public static void main(String[] args) { |
| 3 | System.out.println("Eduinq Print LCS"); |
| 4 | String s1="Eduinq", s2="Enquiry"; |
| 5 | int m=s1.length(), n=s2.length(); |
| 6 | int[][] dp=new int[m+1][n+1]; |
| 7 | for(int i=1;i<=m;i++){ |
| 8 | for(int j=1;j<=n;j++){ |
| 9 | if(s1.charAt(i-1)==s2.charAt(j-1)) |
| 10 | dp[i][j]=1+dp[i-1][j-1]; |
| 11 | else dp[i][j]=Math.max(dp[i-1][j],dp[i][j-1]); |
| 12 | } |
| 13 | } |
| 14 | int i=m, j=n; |
| 15 | StringBuilder lcs=new StringBuilder(); |
| 16 | while(i>0 && j>0){ |
| 17 | if(s1.charAt(i-1)==s2.charAt(j-1)){ |
| 18 | lcs.insert(0,s1.charAt(i-1)); |
| 19 | i--; j--; |
| 20 | } else if(dp[i-1][j]>dp[i][j-1]) i--; |
| 21 | else j--; |
| 22 | } |
| 23 | System.out.println("Longest common subsequence: "+lcs.toString()); |
| 24 | } |
| 25 | } |
Program Output
Eduinq Print LCS Longest common subsequence: Enq
Explanation
After the DP table storing subsequence lengths is built, a backtracking loop walks from the bottom-right cell, inserting matching characters at the front of the result and moving in the direction of the larger neighboring value, reconstructing the actual longest common subsequence.