Interleaving String

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.

class Solution {
public:
bool isInterleave(string s1, string s2, string s3) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
int N1 = s1.size();
int N2 = s2.size();

if(N1+N2 != s3.size()) return false;

vector<vector<bool>> f(N1+1, vector<bool>(N2+1, 1));

for(int i = 1; i <= N1; i++){
f[i][0] = f[i-1][0] && s3[i-1] == s1[i-1];
}

for(int j = 1; j <= N2; j++){
f[0][j] = f[0][j-1] && s3[j-1] == s2[j-1];
}

for(int i = 1; i <= N1; i++){
for(int j = 1; j <= N2; j++){
f[i][j] = (f[i-1][j] && s3[i+j-1] == s1[i-1]) ||
( f[i][j-1] && s3[i+j-1] == s2[j-1]);
}
}

return f[N1][N2];

}
};