leetcode minimum path sum

class Solution {
public:
    int minPathSum(vector<vector<int> > &grid) 
    {
        int m=grid.size();
        if(m==0)return 0;
        int n=grid[0].size();       
        for(int i=1;i<m;i++)
        grid[i][0]+=grid[i-1][0];
        for(int i=1;i<n;i++)
        grid[0][i]+=grid[0][i-1];
        for(int i=1;i<m;i++)
        {
            for(int j=1;j<n;j++)
            {
                grid[i][j]=grid[i][j]+min(grid[i-1][j],grid[i][j-1]);
            }
        }
        return grid[m-1][n-1];       
    }
};