LeetCode #97: Interleaving String

Description:

Given s1, s2, 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

Solution:

• DP (2d) method
• Time complexity: O(m*n)
• Space complexity: O((m+1)*(n+1))

class Solution(object):
    def isInterleave(self, s1, s2, s3):
        if len(s3) == len(s1) + len(s2):
            table = [[False for i in range(len(s1)+1)] for j in range(len(s2)+1)]
            table[0][0] = True

            for j in range(1, len(s1)+1):
                table[0][j] = table[0][j-1] and (s1[j-1] == s3[j-1])

            for i in range(1, len(s2)+1):
                table[i][0] = table[i-1][0] and (s2[i-1] == s3[i-1])
                for j in range(1, len(s1)+1):
                    table[i][j] = (table[i-1][j] and (s2[i-1] == s3[i+j-1])) or \
                            (table[i][j-1] and (s1[j-1] == s3[i+j-1]))

            return table[-1][-1]
        else:
            return False