Unique Paths

class Solution {public:    int uniquePaths(int m, int n) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        vector<int> col(n+1,0);        vector<vector<int>> Grid(m+1,col);                int i,j;        for(i=1;i<=m;++i){            for(j=1;j<=n;++j){                if(i==1&&j==1)Grid[i][j]=1;                else                Grid[i][j]=Grid[i-1][j]+Grid[i][j-1];            }        }        return Grid[m][n];    }};