牛客题霸 [最长公共子序列] C++题解/答案

题目描述

给定两个字符串str1和str2，输出连个字符串的最长公共子序列。如过最长公共子序列为空，则输出-1。

题解：

dp经典问题

代码：

class Solution {
public:/*** longest common subsequence* @param s1 string字符串 the string* @param s2 string字符串 the string* @return string字符串*/string LCS(string s1, string s2) {// write code hereint len1 = s1.size();int len2 = s2.size();string a=solve(len1,len2,s1,s2);return a;}string solve(int len1,int len2,string s1,string s2){vector<vector<string> > dp(len1 + 1, vector<string>(len2 + 1, ""));string temp,temp1,temp2;for(int i = 1; i <= len1; ++i){for(int j = 1; j <= len2; ++j){if(s1[i - 1] == s2[j - 1]){temp = dp[i - 1][j - 1];temp += s1[i - 1];dp[i][j] = temp;}else{temp1 = dp[i - 1][j];temp2 = dp[i][j - 1];if(temp1.size() > temp2.size()){dp[i][j] = temp1;}else{dp[i][j] = temp2;}}}}if (dp[len1][len2] == "")return "-1";elsereturn dp[len1][len2];}
};