LeetCode——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.

原题链接:https://oj.leetcode.com/problems/triangle/

题目：给定一个三角形，找出从顶部到底部的最短路径和。每一步你可以移动到下一行的邻接数字。

思路：最初的理解是：最短路径和可以看成是找出每一行中的最小值，最后求和。

	public int minimumTotal1(List<List<Integer>> triangle) {
		int sum = 0;
		for (int i = 0; i < triangle.size(); i++) {
			int min = triangle.get(i).get(0);
			for (int j = 0; j < triangle.get(i).size(); j++) {
				if (triangle.get(i).get(j) < min)
					min = triangle.get(i).get(j);
			}
			sum += min;
		}
		return sum;
	}

	public int minimumTotal(List<List<Integer>> triangle) {
	    for(int i = triangle.size() - 2; i >= 0; i--)
	    {
	        for(int j = 0; j < triangle.get(i).size(); j++)
	        {
	            triangle.get(i).set(j, triangle.get(i).get(j) + Math.min(triangle.get(i + 1).get(j), triangle.get(i + 1).get(j + 1)));
	        }
	    }
	    return triangle.get(0).get(0);
	}

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LeetCode——Triangle

原文：http://blog.csdn.net/laozhaokun/article/details/37735623