Interleaving String

Given s1, s2, s3, find whether s3 is formed by the interleaving of s1 and s2.
For example,
Given:
s1 = "aabcc",
s2 = "dbbca",
When s3 = "aadbbcbcac", return true.
When s3 = "aadbbbaccc", return false.

Solution: 1. dp. O(MN) time & space. 'dp[i][j] == true' means that there is at least one way to construct
the string s3[0...i+j-1] by interleaving s1[0...j-1] and s2[0...i-1].
2. Recursion. Okay for Small but TLE for Large Test data.

 1 class Solution {
 2 public:
 3     bool isInterleave(string s1, string s2, string s3) {
 4         int M = s1.size(), N = s2.size(), K = s3.size();
 5         if (M + N != K) return false;
 6         
 7         int dp[N+1][M+1];
 8         for (int i = 1; i <= N; ++i)
 9             dp[i][0] = s2[i-1] == s3[i-1];
10         for (int j = 1; j <= M; ++j)
11             dp[0][j] = s1[j-1] == s3[j-1];
12 
13         for (int i = 1; i <= N; ++i)
14             for (int j = 1; j <= M; ++j)
15                 dp[i][j] = dp[i-1][j] && s2[i-1] == s3[i+j-1] ||
16                            dp[i][j-1] && s1[j-1] == s3[i+j-1];
17 
18         return dp[N][M];
19     }
20 };

 

posted @ 2014-04-24 08:29  beehard  阅读(145)  评论(0)  编辑  收藏  举报