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.

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思路：经典DP动态规划入门问题，

定义状态转移方程f[i][j] = min(f[i-1][j],f[i][j-1])+grid[i][j]

初始状态函数，二维数组f[][]的第一行和第一列

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code 如下：

class Solution{public:    int minPathSum(vector
     
      
        > &grid){        if(grid.size()==0) return 0;        const int m = grid.size();        const int n = grid[0].size();        int f[m][n];        f[0][0] = grid[0][0];        for(int i = 1;i