LeetCode in Kotlin

2349. Design a Number Container System

Medium

Design a number container system that can do the following:

• Insert or Replace a number at the given index in the system.
• Return the smallest index for the given number in the system.

Implement the NumberContainers class:

• NumberContainers() Initializes the number container system.
• void change(int index, int number) Fills the container at index with the number. If there is already a number at that index, replace it.
• int find(int number) Returns the smallest index for the given number, or -1 if there is no index that is filled by number in the system.

Example 1:

Input

[“NumberContainers”, “find”, “change”, “change”, “change”, “change”, “find”, “change”, “find”]

[[], [10], [2, 10], [1, 10], [3, 10], [5, 10], [10], [1, 20], [10]]

Output: [null, -1, null, null, null, null, 1, null, 2]

Explanation:

NumberContainers nc = new NumberContainers();
nc.find(10); // There is no index that is filled with number 10. Therefore, we return -1.
nc.change(2, 10); // Your container at index 2 will be filled with number 10.
nc.change(1, 10); // Your container at index 1 will be filled with number 10.
nc.change(3, 10); // Your container at index 3 will be filled with number 10.
nc.change(5, 10); // Your container at index 5 will be filled with number 10.
nc.find(10); // Number 10 is at the indices 1, 2, 3, and 5. Since the smallest index that is filled with 10 is 1, we return 1.
nc.change(1, 20); // Your container at index 1 will be filled with number 20. Note that index 1 was filled with 10 and then replaced with 20.
nc.find(10); // Number 10 is at the indices 2, 3, and 5. The smallest index that is filled with 10 is 2. Therefore, we return 2. 

Constraints:

• 1 <= index, number <= 109
• At most 105 calls will be made in total to change and find.

Solution

import java.util.TreeSet

class NumberContainers {
    private val indices: MutableMap<Int, TreeSet<Int>> = HashMap()
    private val vals: MutableMap<Int, Int> = HashMap()
    fun change(index: Int, number: Int) {
        if (vals.containsKey(index)) {
            val old = vals[index]!!
            indices[old]!!.remove(index)
            if (indices[old]!!.isEmpty()) {
                indices.remove(old)
            }
        }
        vals[index] = number
        indices.computeIfAbsent(number) { _: Int? -> TreeSet() }.add(index)
    }

    fun find(number: Int): Int {
        return if (indices.containsKey(number)) {
            indices[number]!!.first()
        } else -1
    }
}
/*
 * Your NumberContainers object will be instantiated and called as such:
 * var obj = NumberContainers()
 * obj.change(index,number)
 * var param_2 = obj.find(number)
 */

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