Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.

Note: You can only move either down or right at any point in time.

answer:

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 < n; i ++)            grid[0][i] += grid[0][i - 1];        for(int i = 1; i < m; i ++)            grid[i][0] += grid[i - 1][0];        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];    }        };