题解 | #最长公共子串#

动态规划，dp[i+1][j+1] = dp[i][j] + 1; dp[i][j]之前的公共子串长度

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 maxLength = 0;
        int lastIndex = 0;
        int[][] dp = new int[str1.length()+1][str2.length()+1];
        for(int i = 0;i<str1.length();i++){
            for(int j = 0;j<str2.length();j++){
                if(str1.charAt(i) == str2.charAt(j)){
                    dp[i+1][j+1] = dp[i][j] + 1; 
                    if(dp[i+1][j+1] > maxLength){
                        maxLength = dp[i+1][j+1];
                        lastIndex = i;
                    }
                }
                else{
                    dp[i][j] = 0;
                }
            }
        }
        return str1.substring(lastIndex - maxLength + 1,lastIndex + 1);
    }
}