Leetcode题集——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.

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 min(int a,int b)
    {
       return a<b?a:b; 
    }
    int minPathSum(vector<vector<int> > &grid) 
    {
      int m=grid.size();
      int n=grid[0].size();
      if(grid.empty()||m==0||n==0)
          return 0;
      //边界值单独处理,第0列，第0行。
      for(int i=1;i<m;i++)
          grid[i][0]=grid[i-1][0]+grid[i][0];
      for(int j=1;j<n;j++)
          grid[0][j]=grid[0][j-1]+grid[0][j];
     
      for(int i=1;i<m;i++)
          for(int j=1;j<n;j++)
          {
            grid[i][j]=grid[i][j]+min(grid[i-1][j],grid[i][j-1]);
      }
        
        return grid[m-1][n-1];
    }
};