README.md

135. Candy

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

Solutions (Rust)

1. Solution

impl Solution {
    pub fn candy(ratings: Vec<i32>) -> i32 {
        let mut candies = vec![1; ratings.len()];

        for i in 1..ratings.len() {
            if ratings[i] > ratings[i - 1] {
                candies[i] = candies[i - 1] + 1;
            }
        }
        for i in (0..ratings.len() - 1).rev() {
            if ratings[i] > ratings[i + 1] {
                candies[i] = candies[i].max(candies[i + 1] + 1);
            }
        }

        candies.into_iter().sum()
    }
}