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]

public class Solution {
    public int minPathSum(int[][] grid) {
        if(grid ==null || grid.length==0 ||grid[0].length==0){
            return 0;
        }
        int m = grid.length;
        int n = grid[0].length;
        int[][] dp = new int[m][n];
        dp[0][0]= grid[0][0];
        
        for(int i = 1; i < m ; i++){
            dp[i][0] = dp[i-1][0]+grid[i][0];
        }
        for(int j = 1; j < n ;  j++){
            dp[0][j] = dp[0][j-1] + grid[0][j];
        }
        
        for(int i = 1; i < m ; i++){
            for(int j = 1; j < n; j++){
                dp[i][j] = Math.min(dp[i-1][j], dp[i][j-1]) + grid[i][j];
            }
        }
        return dp[m-1][n-1];
    }
}