[动态规划] leetcode 120 Triangle

problem: https://leetcode.com/problems/triangle/

       非常简单直观的dp，注意下标不要搞错就可以了。

class Solution {
public:
    int minimumTotal(vector<vector<int>>& triangle) {
        if (triangle.size() == 0) return 0;
        vector<int> dp(triangle[triangle.size() - 1].size());
        dp[0] = triangle[0][0];
        for (int i = 1; i < triangle.size(); i++)
        {
            for (int j = triangle[i].size() - 1; j >= 0; j--)
            {
                if (j == triangle[i].size() - 1)
                {
                    dp[j] = triangle[i][j] + dp[j - 1];
                }
                else if (j == 0)
                {
                    dp[j] = triangle[i][j] + dp[j];
                }
                else
                {
                    dp[j] = min(dp[j - 1], dp[j]) + triangle[i][j];
                }
            }
        }
        int m = 10000;
        for (int i = 0; i < dp.size(); i++)
        {
            if (dp[i] < m)m = dp[i];
        }
        return m;
    }
};