leetcode 135. Candy

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解决一个有趣的问题：如何在确保每个孩子至少获得一颗糖果的同时，让评分较高的孩子得到比邻居更多的糖果？通过两次遍历的方法实现最小糖果数目的分配。

135. Candy

There are N children standing in a line. Each child is assigned a rating value.

You are giving candies to these children subjected to the following requirements:

Each child must have at least one candy.
Children with a higher rating get more candies than their neighbors.

What is the minimum candies you must give?

本题的关键在于如果ratings小，那么拿到的candy就比两边少，所以应该想到左右两个方向各来一次遍历。

class Solution {
public:
    int candy(vector<int>& ratings) 
    {
        int n = ratings.size();
        vector<int> A(n, 1);
        
        for (int i = 1; i < n; i++)
        {
            if (ratings[i] > ratings[i-1])
               A[i] = A[i-1] + 1;
        }
        
        for (int i = n - 2; i >= 0; i--)
        {
            if (ratings[i] > ratings[i+1] && A[i] < A[i+1] + 1)
                A[i] = A[i+1] + 1;
        }
        
        return accumulate(A.begin(), A.end(), 0);
    }
};