Minimum Path Sum

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.

比较简单：

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

python 

class Solution:    # @param grid, a list of lists of integers    # @return an integer    def minPathSum(self, grid):        m = len(grid)        n = len(grid[0])                all = grid[:]        for i in range(1,n):            all[0][i] += all[0][i-1]                for i in range(1,m):            all[i][0] += all[i-1][0]                for i in range(1,m):            for j in range(1,n):                all[i][j] += min(all[i-1][j],all[i][j-1])                return all[m-1][n-1]                        

总结：

1. 使用 const 比较好，传进来的参数不被修改

2. 注意循环的其始