[LintCode] Candy 分糖果问题

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?

Have you met this question in a real interview?

Yes

Example

Given ratings = [1, 2], return 3.

Given ratings = [1, 1, 1], return 3.

Given ratings = [1, 2, 2], return 4. ([1,2,1]).

LeetCode上的原题，请参见我之前的博客Candy。

class Solution {
public:
    /**
     * @param ratings Children's ratings
     * @return the minimum candies you must give
     */
    int candy(vector<int>& ratings) {
        if (ratings.empty()) return ;
        int res = , n = ratings.size();
        vector<int> dp(n, ), dp2 = dp;
        for (int i = ; i < n; ++i) {
            if (ratings[i] > ratings[i - ]) dp[i] = dp[i - ] + ;
            else dp[i] = ;
        }
        for (int i = n - ; i >= ; --i) {
            if (ratings[i] > ratings[i + ]) dp2[i] = dp2[i + ] + ;
            else dp2[i] = ;
        }
        for (int i = ; i < n; ++i) {
            res += max(dp[i], dp2[i]);
        }
        return res;
    }
};