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.
这个题跟之前的这道题几乎是一样的。之前做的用的二维数组保存的，其实由底向上计算，只需要一维数组即可。
public int minimumTotal(List<List<Integer>> triangle) { if(triangle==null||triangle.size()==0){ return 0; } if(triangle.size()==1){ return triangle.get(0).get(0); } int[] res = new int[triangle.size()]; for(int i=0;i<triangle.size();i++){ res[i]=triangle.get(triangle.size()-1).get(i); } for(int i=triangle.size()-2;i>=0;i--){ List<Integer> row = triangle.get(i); for(int j = 0;j<row.size();j++){ res[j]=Math.min(res[j],res[j+1])+row.get(j); } } return res[0]; }
原文：http://www.cnblogs.com/aboutblank/p/4409921.html