LeetCode 64 Minimum Path Sum

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.

先算每行第一个，和每列第一个，然后每一个dp里都是取前一个左边或者上边一个最小值加上当前值。返回[m-1][n-1]

 1 public class Solution {

 2     public int minPathSum(int[][] grid) {

 3         if(grid ==null || grid.length==0 ||grid[0].length==0){

 4             return 0;

 5         }

 6         int m = grid.length;

 7         int n = grid[0].length;

 8         int[][] dp = new int[m][n];

 9         dp[0][0]= grid[0][0];

10         

11         for(int i = 1; i < m ; i++){

12             dp[i][0] = dp[i-1][0]+grid[i][0];

13         }

14         for(int j = 1; j < n ;  j++){

15             dp[0][j] = dp[0][j-1] + grid[0][j];

16         }

17         

18         for(int i = 1; i < m ; i++){

19             for(int j = 1; j < n; j++){

20                 dp[i][j] = Math.min(dp[i-1][j], dp[i][j-1]) + grid[i][j];

21             }

22         }

23         return dp[m-1][n-1];

24     }

25 }