一、题目

Given two strings text1 and text2, return the length of their longest common subsequence. If there is no common subsequence, return 0.

A subsequence of a string is a new string generated from the original string with some characters (can be none) deleted without changing the relative order of the remaining characters.

For example, “ace” is a subsequence of “abcde”.
A common subsequence of two strings is a subsequence that is common to both strings.

Example 1:

Input: text1 = “abcde”, text2 = “ace”
Output: 3
Explanation: The longest common subsequence is “ace” and its length is 3.
Example 2:

Input: text1 = “abc”, text2 = “abc”
Output: 3
Explanation: The longest common subsequence is “abc” and its length is 3.
Example 3:

Input: text1 = “abc”, text2 = “def”
Output: 0
Explanation: There is no such common subsequence, so the result is 0.

Constraints:

1 <= text1.length, text2.length <= 1000
text1 and text2 consist of only lowercase English characters.

二、题解

class Solution {
public:int longestCommonSubsequence(string text1, string text2) {int n = text1.size(),m = text2.size();vector<vector<int>> dp(n+1,vector<int>(m+1,0));for(int i = 1;i <= n;i++){for(int j = 1;j <= m;j++){if(text1[i - 1] == text2[j - 1]) dp[i][j] = 1 + dp[i-1][j-1];else dp[i][j] = max(dp[i-1][j],dp[i][j-1]);}}return dp[n][m];}
};