LeetCode 135. Candy

Description

https://leetcode.com/problems/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.

Explanation

Python Solution

class Solution:
    def candy(self, ratings: List[int]) -> int:
        candies = [1 for i in range(len(ratings))]
        
        for i in range(1, len(ratings)):
            if ratings[i] > ratings[i - 1]:
                candies[i] = candies[i - 1] + 1
        
        for i in range(len(ratings) - 2, -1, -1):
            if ratings[i + 1] < ratings[i] and candies[i + 1] >= candies[i]:
                candies[i] = candies[i + 1] + 1
                
        return sum(candies)
            
        
  • Time Complexity: ~N
  • Space Complexity: ~N

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