120. Triangle Medium

Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.

思路：题目就是说从三角形顶端向下走，找到一条路使得和最小。这是个二维动态规划问题，我们将其分解为多个类似的子问题：寻找每个点到最低端的最小值，从底部开始向上找，这样就使得顶端点的值为我们所需要的最小值。

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], triangle[i + 1][j + 1]);            }        }        return triangle[0][0];    }};