LeetCode in Kotlin

1424. Diagonal Traverse II

Medium

Given a 2D integer array nums, return all elements of nums in diagonal order as shown in the below images.

Example 1:

Input: nums = [[1,2,3],[4,5,6],[7,8,9]]

Output: [1,4,2,7,5,3,8,6,9]

Example 2:

Input: nums = [[1,2,3,4,5],[6,7],[8],[9,10,11],[12,13,14,15,16]]

Output: [1,6,2,8,7,3,9,4,12,10,5,13,11,14,15,16]

Constraints:

• 1 <= nums.length <= 105
• 1 <= nums[i].length <= 105
• 1 <= sum(nums[i].length) <= 105
• 1 <= nums[i][j] <= 105

Solution

import java.util.ArrayDeque
import java.util.Objects

class Solution {
    fun findDiagonalOrder(nums: List<List<Int>>): IntArray {
        val ans: MutableList<Int> = ArrayList()
        val queue = ArrayDeque<Iterator<Int>>()
        var pos = 0
        do {
            if (pos < nums.size) {
                queue.offerFirst(nums[pos].iterator())
            }
            var sz = queue.size
            while (--sz >= 0) {
                val cur = queue.poll()
                ans.add(Objects.requireNonNull(cur).next())
                if (cur.hasNext()) {
                    queue.offer(cur)
                }
            }
            pos++
        } while (queue.isNotEmpty() || pos < nums.size)
        return ans.stream().mapToInt { o: Int? -> o!! }.toArray()
    }
}

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