题解 | #最长公共子串#

import java.util.*;


public class Solution {
    /**
     * longest common substring
     * @param str1 string字符串 the string
     * @param str2 string字符串 the string
     * @return string字符串
     */
    public String LCS (String str1, String str2) {
        // write code here

        int m = str1.length();
        int n = str2.length();

        int dp[][] = new int[m+1][n+1];

        int max = -1;

        int target_x = 0;
       // int target_y = 0;

        for(int i = 1 ; i <= m ; i++){
            for(int j = 1 ; j <= n ; j++){
                if(str1.charAt(i-1) == str2.charAt(j-1)){
                    dp[i][j] = dp[i-1][j-1] + 1;
                    if(dp[i][j] > max){
                        max = dp[i][j]; 
                        target_x = i;
                       // target_y = j;   
                    }
                }else{
                    continue;
                }
            }
        }

        StringBuilder s = new StringBuilder("");

        while(max != 0){
            s.append(str1.charAt(target_x-1));
            target_x--;
            max--;
        }
        String res = s.reverse().toString();

        return res;
    }
}