LeetCode120 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.（Medium）

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：

经典的动态规划题，可以有自顶向下，自底向上的解法，是自己学动态规划的第一道题，就不分析了，写一个自底向上的解法。

代码：

 class Solution {
 public:
     int minimumTotal(vector<vector<int>>& triangle) {
         int sz = triangle.size();
         if (sz == ) {
             return ;
         }
         int dp[sz][sz];
         for (int i = ; i < sz; ++i) {
             dp[sz - ][i] = triangle[sz - ][i];
         }
         for (int i = sz - ; i >= ; --i) {
             for (int j = ; j <= i; ++j) {
                 dp[i][j] = min(dp[i + ][j], dp[i + ][j + ]) + triangle[i][j];
             }
         }
         return dp[][];
     }
 };