LeetCode – Refresh – Interleaving String

 1 class Solution {
 2 public:
 3     bool isInterleave(string s1, string s2, string s3) {
 4         int l1 = s1.size(), l2 = s2.size(), l3 = s3.size();
 5         if (l3 != l2 + l1) return false;
 6         vector<vector<bool> > dp(l1+1, vector<bool> (l2+1, false));
 7         dp[0][0] = true;
 8         for (int i = 1; i <= l1; i++) dp[i][0] = dp[i-1][0] && s1[i-1] == s3[i-1];
 9         for (int i = 1; i <= l2; i++) dp[0][i] = dp[0][i-1] && s2[i-1] == s3[i-1];
10         for (int i = 1; i <= l1; i++) {
11             for (int j = 1; j <= l2; j++) {
12                 dp[i][j] = ((dp[i-1][j] && s1[i-1] == s3[i+j-1]) ||
13                             (dp[i][j-1] && s2[j-1] == s3[i+j-1]) ||
14                             (dp[i-1][j-1] && s1[i-1] == s3[i+j-1] && s2[j-1] == s3[i+j-2]) ||
15                             (dp[i-1][j-1] && s1[i-1] == s3[i+j-2] && s2[j-1] == s3[i+j-1]));
16             }
17         }
18         return dp[l1][l2];
19     }
20 };