[leetcode]120. Triangle

题目：

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.

分析：动态规划，从后往前推，会轻松很多。

代码：

class Solution {
public:
int minimumTotal(vector<vector<int> > &triangle) {
for (int i = triangle.size() - 2; i >= 0; --i)
for (int j = 0; j <= i; ++j){

triangle[i][j] +=min(triangle[i+1][j+1],triangle[i+1][j]);
}

return triangle[0][0];
}
};

PS.手机屏幕碎了，不开心