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135. Candy

Difficulty Topics

Description

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

candy.py
class Solution:
    def candy(self, ratings: List[int]) -> int:
        n = len(ratings)

        A = [(x, i) for i, x in enumerate(ratings)]
        A.sort()
        candies = [1] * n

        for x, i in A:
            current = candies[i]

            if i - 1 >= 0 and ratings[i - 1] > x:
                candies[i - 1] = max(candies[i - 1], current + 1)

            if i + 1 < n and ratings[i + 1] > x:
                candies[i + 1] = max(candies[i + 1], current + 1)

        return sum(candies)