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?
使用迭代的方法, 时间复杂度 O(n),空间复杂度 O(n)

// LeetCode, Candy
// 时间复杂度 O(n),空间复杂度 O(n)
class Solution {
    public:
        int candy(vector &ratings) {
            const int n = ratings.size();
            vector increment(n);
            // 左右各扫描一遍
            for (int i = 1, inc = 1; i < n; i++) {                 
                if (ratings[i] > ratings[i - 1])
                    increment[i] = max(inc++, increment[i]);
                else
                    inc = 1;
            }
            for (int i = n - 2, inc = 1; i >= 0; i--) {
                if (ratings[i] > ratings[i + 1])
                    increment[i] = max(inc++, increment[i]);
                else
                    inc = 1;
            }
            // 初始值为 n,因为每个小朋友至少一颗糖
            return accumulate(&increment[0], &increment[0]+n, n);
        }
};