编程练习（第十一周）

题目来源：https://leetcode.com

97. Interleaving String

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• Total Accepted: 67459
• Total Submissions: 277962
• Difficulty: Hard
• Contributor: LeetCode

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.

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题解：

    bool isInterleave(string s1, string s2, string s3) {        int n1=s1.size(),n2=s2.size(),n3=s3.size();        if(n1+n2!=n3) return false;        vector<int> mp(255,0);        for(int i=0;i<n1;i++) mp[s1[i]]++;        for(int i=0;i<n2;i++) mp[s2[i]]++;        for(int i=0;i<n3;i++){            mp[s3[i]]--;            if(mp[s3[i]]<0) return false;        }        vector<vector<int> >dp(n1+1,vector<int>(n2+1,0));        dp[0][0] = 1;        for(int len = 1;len<=n3;len++){            for(int l=max(0,len-n2);l<=len&&l<=n1;l++){                if(l>0 && s1[l-1]==s3[len-1]) dp[l][len-l] |= dp[l-1][len-l];                if(len-l>0 && s2[len-l-1]==s3[len-1]) dp[l][len-l] |= dp[l][len-l-1];            }        }        return dp[n1][n2]==1;    }