LeetCode-in-Java

135. Candy

Hard

There are n children standing in a line. Each child is assigned a rating value given in the integer array ratings.

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.

Return the minimum number of candies you need to have to distribute the candies to the children.

Example 1:

Input: ratings = [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: ratings = [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.

Constraints:

• n == ratings.length
• 1 <= n <= 2 * 104
• 0 <= ratings[i] <= 2 * 104

Solution

import java.util.Arrays;

public class Solution {
    public int candy(int[] ratings) {
        int[] candies = new int[ratings.length];
        Arrays.fill(candies, 1);
        for (int i = 0; i < ratings.length - 1; i++) {
            if (ratings[i + 1] > ratings[i]) {
                candies[i + 1] = candies[i] + 1;
            }
        }
        for (int i = ratings.length - 1; i > 0; i--) {
            if (ratings[i - 1] > ratings[i] && candies[i - 1] < candies[i] + 1) {
                candies[i - 1] = candies[i] + 1;
            }
        }
        int total = 0;
        for (int candy : candies) {
            total += candy;
        }
        return total;
    }
}