64. Minimum Path Sum

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