【DP】1143.最长公共子序列

题目

法1：DP

基础算法，必须掌握！！！

Python

class Solution:
    def longestCommonSubsequence(self, text1: str, text2: str) -> int:
        m, n = len(text1), len(text2)
        dp = [[0]*(n+1) for _ in range(m+1)] # dp[i][j]表示前i/j个公共长度
        for i in range(1, m+1):
            for j in range(1, n+1):
                if text1[i-1] == text2[j-1]:
                    dp[i][j] = dp[i-1][j-1] + 1
                else:
                    dp[i][j] = max(dp[i][j-1], dp[i-1][j])
        
        return dp[m][n]

Java

class Solution {
    public int longestCommonSubsequence(String text1, String text2) {
        int m = text1.length() + 1, n = text2.length() + 1;
        int[][] dp = new int[m][n];
        for (int i = 1; i < m; ++i) {
            for (int j = 1; j < n; ++j) {
                if (text1.charAt(i - 1) == text2.charAt(j - 1)) {
                    dp[i][j] = dp[i - 1][j - 1] + 1;
                } else {
                    dp[i][j] = Math.max(dp[i - 1][j], dp[i][j - 1]);
                }
            }
        }

        return dp[m - 1][n - 1];
    }
}