LeetCode - Interleaving String 题解

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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.

分析

令f[i][j]表示s1的1.,i个和s2的1..j个能否interleave出s3的1..i+j

f[i][j] = (f[i-1][j] && s1[i] == s3[i+j]) || (f[i][j-1] && s2[j] == s3[i+j])

class Solution {
public:
    bool isInterleave(string s1, string s2, string s3) {
        int l1 = s1.length(), l2 = s2.length(), l3 = s3.length();
        if(l1 + l2 != l3)
            return false;
        vector<vector<bool> > f(l1 + 1);
        for(auto &v:f)
            v = vector<bool> (l2 + 1,false);
        f[0][0] = true;
        for(int j = 1; j <= l2; j++)
            f[0][j] = f[0][j - 1] && (s2[j - 1] == s3[j - 1]);
        for(int i = 1; i <= l1; i++){
            f[i][0] = f[i - 1][0] && (s1[i - 1] == s3[i - 1]);
            for(int j = 1; j <= l2; j++){
                f[i][j] = (f[i - 1][j] && (s1[i - 1] == s3[i + j - 1]))
                       || (f[i][j - 1] && (s2[j - 1] == s3[i + j - 1]));
            }
        }
        return f[l1][l2];
    }
};