If numRows > 0,this function will not get the result, as u know,I omit the code "return result". But I got AC 4 this code. Who can help me explain y?

```
class Solution {
public:
vector<vector<int> > generate(int numRows) {
vector<vector<int> > result;
if(numRows <= 0)return result;
vector<int> tmp1;
vector<int> tmp2;
for(int i = 1; i <= numRows;i++)
{
tmp2.clear();
for(int j = 0; j < i;j++){
if(j == 0 || j == i - 1)tmp2.push_back(1);
else tmp2.push_back(tmp1[j] + tmp1[j - 1]);
}
tmp1 = tmp2;
result.push_back(tmp1);
}
//return result;
}
};
```