LeetCode/135_Candy.py at main · AnmolPatel20/LeetCode · GitHub

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"""
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
"""

class Solution:
    def candy(self, ratings: List[int]) -> int:
        n = len(ratings)
        candies = [1] * n  #All the children get one candies

        for i in range(1,n):  #left to right
            if ratings[i] > ratings[i-1]:
                candies[i] = candies[i-1]+1

        for i in range(n-2,-1,-1):    #reverse     #right to left
            if ratings[i] > ratings[i+1]:
                candies[i] = max(candies[i], candies[i+1]+1)

        return sum(candies)