leetcode 120. Triangle

Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.For example, given the following triangle[     [2],    [3,4],   [6,5,7],  [4,1,8,3]]The minimum path sum from top to bottom is 11 (i.e., 2 + 3 + 5 + 1 = 11).Note:Bonus point if you are able to do this using only O(n) extra space, where n is the total number of rows in the triangle.

可以考虑从下至上计算，代码给的比较清楚了

public class Solution {    public int minimumTotal(List<List<Integer>> triangle) {        if(triangle==null) return 0;        int w = triangle.size();        int h = triangle.get(w-1).size();        int[][] dp = new int[w][h];        for(int i=0; i < h; i++){            dp[w-1][i] = triangle.get(w-1).get(i);        }        for(int i = w-2; i >=0 ; i--){            for(int j=0; j < i+1; j++){                dp[i][j] = triangle.get(i).get(j) + Math.min(dp[i+1][j], dp[i+1][j+1]);            }        }        return dp[0][0];    }}