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Minimum Path Sum <leetcode>

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:看到这道题想到两种方法,第一种是分支限界,不过时间复杂度比较高,估计会超时,另一种方法是动态规划,时间复杂度为O(m*n,代码如下:

 1 class Solution { 2 public: 3     vector<vector<int>>  mi; 4     int minPathSum(vector<vector<int> > &grid) { 5         mi=grid; 6         for(int i=1;i<grid[0].size();i++) 7         { 8             mi[0][i]=mi[0][i-1]+mi[0][i]; 9         }10         for(int i=1;i<grid.size();i++)11         {12             mi[i][0]=mi[i-1][0]+mi[i][0];13             for(int j=1;j<grid[0].size();j++)14             {15                 mi[i][j]=min(mi[i-1][j],mi[i][j-1])+mi[i][j];16             }17         }18         return mi[grid.size()-1][grid[0].size()-1];19     }20 };

 

Minimum Path Sum <leetcode>