问题分析

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?

问题分析

我想的思路超时了，于是到网上找了解题报告，具体做法为两遍遍历。首先从左向右遍历ratings数组，若本身比左邻居排名高，则将自身candy数设为左邻居值+1；然后从右向左遍历ratings数组，若本身比右邻居排名高，且当前candy没有比右邻居多，则将自身candy数设为右邻居值+1。

AC代码

class Solution(object):
    def candy(self, ratings):
        """
        :type ratings: List[int]
        :rtype: int
        """
        n = len(ratings)
        if n < 2:
            return n
        cd = [1 for i in range(n)]
        for i in range(1, n):
            if ratings[i] > ratings[i-1]:
                cd[i] = cd[i-1] + 1
        for i in range(n-2, -1, -1):
            if ratings[i] > ratings[i+1] and cd[i] < cd[i+1] + 1:
                cd[i] = cd[i+1] + 1
        return sum(cd)

Runtime: 92 ms, which beats 65.71% of Python submissions.