【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?

class Solution {
public:
    int candy(vector<int> &ratings) {
        int result = 0;
        vector<int> candy(ratings.size(), 0);
        for (int i = 0; i < ratings.size(); ++i) {
            result += solve(ratings, candy, i);
        }
        return result;
    }
private:
    int solve(vector<int> &ratings, vector<int> &candy, int i) {
        if (candy[i] != 0) return candy[i];
        candy[i] = 1;
        if (i < ratings.size() - 1 && ratings[i] > ratings[i + 1]) {
            candy[i] = max(candy[i], solve(ratings, candy, i + 1) + 1);
        } 
        if (i > 0 && ratings[i] > ratings[i - 1]) {
            candy[i] = max(candy[i], solve(ratings, candy, i - 1) + 1);
        }
        return candy[i];
    }
};

先把所有小孩分得的糖初始化为1，然后当糖的数目不能满足左右两边的约束时增加糖的数量，直到符合条件。递归求解。