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.

思路：此题和前面几个机器人的题很相像。仅仅是变化了一点。详细代码和凝视例如以下：

public class Solution {
    public int minPathSum(int[][] grid) {
        //动态规划思想
        //选取到本点的最小值（从上方和左方来的最小值）
        for(int i = 0; i < grid.length; i++)
            for(int j = 0; j < grid[0].length; j++){
                if(i > 0 && j > 0)//分三种情况，第二行第二列之后
                    grid[i][j] += Math.min(grid[i-1][j],grid[i][j-1]);
                else if(i == 0 && j > 0)//第一行
                    grid[i][j] += grid[i][j-1];
                else if(i > 0 && j==0)//第一列
                    grid[i][j] += grid[i-1][j];
            }
        //返回最后一个值
        return grid[grid.length-1][grid[0].length-1];
    }
}