[LeetCode] 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?

Solution:

首先设每个孩子得到一个糖果。然后从前往后扫一遍，如果当前孩子比前一个孩子rating高，但是糖却没有他多，则让该孩子比前一个孩子多拿一个糖。一遍扫完后，满足所有rating高的孩子都比自己的左邻居糖多。然后再从后往前扫一遍，如果当前孩子比后一个孩子rating高，但是糖没有他多，则让该孩子比后一个孩子多拿一个糖。这一遍扫完，满足所有rating高的孩子都比自己的右邻居糖多。最后求和即可。

class Solution {
public:
    int candy(vector<int> &ratings)
    {
        int len = ratings.size(), *num = new int[len];
        if(len <= 1) return len;
        for(int i = 0;i < len;i++)
            num[i] = 1;
        for(int i = 1;i < len;i++)
            if(ratings[i] > ratings[i - 1] && num[i] <= num[i - 1])
                num[i] = num[i - 1] + 1;
        for(int i = len - 2;i >= 0;i--)
            if(ratings[i] > ratings[i + 1] && num[i] <= num[i + 1])
                num[i] = num[i + 1] + 1;
        int ans = 0;
        for(int i = 0;i < len;i++)
            ans += num[i];
        return ans;
    }
};