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.

题目解析：

找一条路径，从左上到右下使其和最小。

还是利用动态规划：f[i][j] = min(f[i-1][j], f[i][j-1]) + a[i][j]

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

        return grid[row-1][col-1];
    }
};