135. 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?

Example 1:

Input: [1,0,2]
Output: 5
Explanation: You can allocate to the first, second and third child with 2, 1, 2 candies respectively.

Example 2:

Input: [1,2,2]
Output: 4
Explanation: You can allocate to the first, second and third child with 1, 2, 1 candies respectively.
             The third child gets 1 candy because it satisfies the above two conditions.

#include <iostream>
#include <vector>

using namespace std;

int candy(vector<int>& ratings){
    vector<int> can(ratings.size(), 1);
    int sum = 0;
    for(int i = 1; i < ratings.size(); ++i){
        if(ratings[i] > ratings[i - 1]){
            can[i] = can[i - 1] + 1;
        }
    }
    for(int i = ratings.size() - 2; i >= 0; --i){
        if(ratings[i] > ratings[i + 1])
            can[i] = max(can[i], can[i + 1] + 1);
        sum += can[i];
    }
    return sum + can[ratings.size() - 1];
}