135. Candy

Description

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?

Constraints

Approach

Links

• GeeksforGeeks

• Leetcode

• ProgramCreek

• YouTube

Examples

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.

Solutions

Solution 1

/**
 * Time complexity : 
 * Space complexity : 
 */

class Solution {
    public int candy(int[] ratings) {
        if(ratings.length == 0) return 0;
        int n = ratings.length;
        int[] arrLtoR = new int[n];
        int[] arrRtoL = new int[n];
        arrLtoR[0] = 1;
        arrRtoL[n-1] = 1;
        
        for(int i = 1; i < n; i++) {
            arrLtoR[i] = (ratings[i-1] < ratings[i])? arrLtoR[i-1]+1: 1;
            arrRtoL[n-i-1] = (ratings[n-i-1] > ratings[n-i])? arrRtoL[n-i]+1: 1;
        }
        
        int total = 0;
        for(int i = 0; i < n; i++) {
            total += Math.max(arrLtoR[i], arrRtoL[i]);
        }
        return total;
    }
}

Follow up