【leetcode】Interleaving String

 1 class Solution {
 2 public:
 3     bool isInterleave(string s1, string s2, string s3) {
 4         
 5         int n1=s1.length();
 6         int n2=s2.length();
 7         int n3=s3.length();
 8         
 9         if(n1+n2!=n3)
10         {
11             return false;
12         }
13         
14         vector<vector<bool> > dp(n1+1,vector<bool>(n2+1,false));
15         
16         dp[0][0]=true;
17         
18         for(int i=1;i<=n1;i++)
19         {
20             dp[i][0]=dp[i-1][0]&&s1[i-1]==s3[i-1];
21         }
22         
23         for(int j=1;j<=n2;j++)
24         {
25             dp[0][j]=dp[0][j-1]&&s2[j-1]==s3[j-1];
26         }
27         
28         for(int i=1;i<=n1;i++)
29         {
30             for(int j=1;j<=n2;j++)
31             {
32                 dp[i][j]=(dp[i-1][j]&&s1[i-1]==s3[i+j-1])||(dp[i][j-1]&&s2[j-1]==s3[i+j-1]);
33             }
34         }
35         
36         return dp[n1][n2];
37     }
38 };