LeetCode in Kotlin

2929. Distribute Candies Among Children II

Medium

You are given two positive integers n and limit.

Return the total number of ways to distribute n candies among 3 children such that no child gets more than limit candies.

Example 1:

Input: n = 5, limit = 2

Output: 3

Explanation: There are 3 ways to distribute 5 candies such that no child gets more than 2 candies: (1, 2, 2), (2, 1, 2) and (2, 2, 1).

Example 2:

Input: n = 3, limit = 3

Output: 10

Explanation: There are 10 ways to distribute 3 candies such that no child gets more than 3 candies: (0, 0, 3), (0, 1, 2), (0, 2, 1), (0, 3, 0), (1, 0, 2), (1, 1, 1), (1, 2, 0), (2, 0, 1), (2, 1, 0) and (3, 0, 0).

Constraints:

• 1 <= n <= 106
• 1 <= limit <= 106

Solution

import kotlin.math.min

class Solution {
    fun distributeCandies(n: Int, limit: Int): Long {
        var ans: Long = 0
        for (i in 0..min(n, limit)) {
            var rem = (n - i).toLong()
            if (rem > 2 * limit) continue
            // second student
            val max = min(limit.toLong(), rem)
            // for third student
            rem -= max
            // if remain is grater than limit cant possible to arrange;
            // if(rem <= limit) than max - rem combination
            if (rem <= limit) ans = ans + max - rem + 1
        }
        return ans
    }
}

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