Leetcode 97. Interleaving String

Seawolf

Given s1, s2, and s3, find whether s3 is formed by the interleaving of s1 and s2.



Example 1:



Input: s1 = "aabcc", s2 = "dbbca", s3 = "aadbbcbcac"
Output: true
Example 2:

Input: s1 = "aabcc", s2 = "dbbca", s3 = "aadbbbaccc"
Output: false
Example 3:

Input: s1 = "", s2 = "", s3 = ""
Output: true


Constraints:

0 <= s1.length, s2.length <= 100
0 <= s3.length <= 200
s1, s2, and s3 consist of lower-case English letters.

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 for _ in range(n + 1)] for _ in range(m + 1)]
        
        for i in range(m + 1):
            for j in range(n + 1):
                if i == 0 and j == 0:
                    dp[i][j] = True
                    continue
                
                dp[i][j] = False
                
                if i > 0 and s3[i + j - 1] == s1[i - 1]:
                    dp[i][j] |= dp[i - 1][j]
                
                if j > 0 and s3[i + j - 1] == s2[j - 1]:
                    dp[i][j] |= dp[i][j - 1]
        
        return dp[m][n]