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.

从底向上，保存每一层的最小和，最后到顶就剩一个了。

class Solution {public:int minimumTotal(vector<vector<int> > &triangle) {if (triangle.empty())return 0;int n = triangle.size();vector<int> ivec(triangle.back().begin(), triangle.back().end());for (int i = n - 2; i >= 0; i--) {for (int j = 0; j <= i; j++) {ivec[j] = min(ivec[j], ivec[j + 1]) + triangle[i][j];}}return ivec[0];}};