leetcode 135. Candy

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);
}
};