一、题目内容

二、题解

解法1：

思路

二维动态规划

代码

public class Solution {
    public String LCS (String s1, String s2) {
        // write code here
        int len1 = s1.length(),len2 = s2.length();
        if(len1 == 0 || len2 == 0){
            return "-1";
        }
        int[][] dp = new int[len1+1][len2+1];
        for(int i = 0;i<=len1;i++){
            for(int j = 0;j<=len2;j++){
                if(i == 0 || j == 0){
                    dp[i][j] = 0;
                }else if(s1.charAt(i-1) == s2.charAt(j-1)){
                    dp[i][j] = dp[i-1][j-1] + 1;
                }else{
                    dp[i][j] = Math.max(dp[i][j-1],dp[i-1][j]);
                }
            }
        }
        if(dp[len1-1][len2-1] == 0){
            return "-1";
        }
        StringBuilder result = new StringBuilder();
        int i = len1, j = len2;
        while (i > 0 && j > 0) {
            if (s1.charAt(i-1) == s2.charAt(j-1)) {
                result.append(s1.charAt(i-1));
                i--;
                j--;
            } else {
                if (dp[i][j-1] > dp[i-1][j]) {
                    j--;
                } else {
                    i--;
                }
            }
        }
        return result.reverse().toString();
    }
}