leetcode[97]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) {
if(s1.size()+s2.size()!=s3.size())return false;
vector<vector<bool>> f(s1.size()+1,vector<bool> (s2.size()+1,false));
f[0][0]=true;
for(int i=1;i<=s1.size();i++)
{
f[i][0]=(f[i-1][0]&&s1[i-1]==s3[i-1]);
}
for(int j=1;j<=s2.size();j++)
{
f[0][j]=(f[0][j-1]&&s2[j-1]==s3[j-1]);
}
for(int i=1;i<=s1.size();i++)
{
for(int j=1;j<=s2.size();j++)
{
f[i][j]=(f[i][j-1]&&s2[j-1]==s3[i+j-1])||(f[i-1][j]&&s1[i-1]==s3[i+j-1]);
}
}
return f[s1.size()][s2.size()];
}
};