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.
思路:
其实是一个动态规划问题:设o1, o2, o3分别为在s1, s2, s3上的下标:
is_interleaving(o1, o2, o3) = is_interleaving(o1-1, o2, o3) || is_interleaving(o1, o2-1, o3);
题解:
class Solution { public: bool is_interleaving( const string& s1, const string& s2, const string& s3, int o1, int o2, int o3) { if (o3 < 0) return true; else return (s1[o1]==s3[o3] ? is_interleaving(s1, s2, s3, o1 - 1, o2, o3 - 1) : false) || (s2[o2]==s3[o3] ? is_interleaving(s1, s2, s3, o1, o2 - 1, o3 - 1) : false); } bool isInterleave(string s1, string s2, string s3) { if (s1.size() + s2.size() != s3.size()) return false; return is_interleaving(s1, s2, s3, s1.size() - 1, s2.size() - 1, s3.size() - 1); } };