LeetCode进阶之路（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.

题目：还是寻找路径，不过这次是寻找最短的路径。

思路：还是使用动态规划。

public class Solution {
    public int minPathSum(int[][] grid) {
    if(grid == null || grid.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];    
 
    // initialize top row
    for(int i=1; i<n; i++){
        dp[0][i] = dp[0][i-1] + grid[0][i];
    }
 
    // initialize left column
    for(int j=1; j<m; j++){
        dp[j][0] = dp[j-1][0] + grid[j][0];
    }
 
    // fill up the dp table
    for(int i=1; i<m; i++){
        for(int j=1; j<n; j++){
            if(dp[i-1][j] > dp[i][j-1]){
                dp[i][j] = dp[i][j-1] + grid[i][j];
            }else{
                dp[i][j] = dp[i-1][j] + grid[i][j];
            }
        }
    }
 
    return dp[m-1][n-1];
}
}

种一棵树最好的时间是十年前，其次是现在！