Leetcode 97.交错字符串（Interleaving String）

Leetcode 97.交错字符串

1 题目描述（Leetcode题目链接）

  给定三个字符串 s1, s2, s3, 验证 s3 是否是由 s1 和 s2 交错组成的。

输入: s1 = "aabcc", s2 = "dbbca", s3 = "aadbbcbcac"
输出: true

输入: s1 = "aabcc", s2 = "dbbca", s3 = "aadbbbaccc"
输出: false

2 题解

  动态规划，定义$dp[i][j]$dp[i][j]为$s_1$s1​的前$i$i个字符与$s_2$s2​的前$j$j个字符能否交错组成$s_3$s3​的前$i+j$i+j个字符。分析比较容易。

class Solution:
    def isInterleave(self, s1: str, s2: str, s3: str) -> bool:
        m, n = len(s1), len(s2)
        if m + n != len(s3):
            return False
        dp = [([False]*(n+1)) for _ in range(m+1)]
        dp[0][0] = True
        for i in range(1, n+1):
            dp[0][i] = (s2[i-1] == s3[i-1]) and dp[0][i-1]
        for i in range(1, m+1):
            dp[i][0] = (s1[i-1] == s3[i-1]) and dp[i-1][0]
        for i in range(1, m+1):
            for j in range(1, n+1):
                dp[i][j] = ((s3[i+j-1] == s1[i-1]) and dp[i-1][j]) or ((s3[i+j-1] == s2[j-1]) and dp[i][j-1])
        return dp[-1][-1]