How hard is LeetCode 1424. Diagonal Traverse II?

LeetCode 1424. Diagonal Traverse II is rated Medium on LeetCode.

What is the time complexity of LeetCode 1424. Diagonal Traverse II?

The Python solution on this page runs in O(n \times \log n), where n is the number of elements in the array \textit{nums}.

What is the space complexity of LeetCode 1424. Diagonal Traverse II?

The Python solution on this page uses O(n) auxiliary space.

What topics does LeetCode 1424. Diagonal Traverse II cover?

LeetCode 1424. Diagonal Traverse II is tagged Array, Sorting and Heap (Priority Queue) on LeetCode.

Diagonal Traverse II — LeetCode 1424 Python Solution

MediumArraySortingHeap (Priority Queue)

Problem: #1424
Pattern: Heap / Priority Queue
Reading time: 2 min
Source: leetcode.com

The problem

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

Example

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

Python solution

Python

class Solution:
    def findDiagonalOrder(self, nums: List[List[int]]) -> List[int]:
        arr = []
        for i, row in enumerate(nums):
            for j, v in enumerate(row):
                arr.append((i + j, j, v))
        arr.sort()
        return [v[2] for v in arr]

Complexity

Measure	Complexity
Time	O(n \times \log n), where n is the number of elements in the array \textit{nums}
Space	O(n) auxiliary

Pattern: Heap / Priority Queue

Keep only the best k elements, or always pull the smallest, in log time. LeetCode 1424. Diagonal Traverse II is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Heap (Priority Queue).

The heap / priority queue guide has the Python template for the pattern and the 163 LeetCode problems that use it.

Frequently asked questions

How hard is LeetCode 1424. Diagonal Traverse II?: LeetCode 1424. Diagonal Traverse II is rated Medium on LeetCode.
What is the time complexity of LeetCode 1424. Diagonal Traverse II?: The Python solution on this page runs in O(n \times \log n), where n is the number of elements in the array \textit{nums}.
What is the space complexity of LeetCode 1424. Diagonal Traverse II?: The Python solution on this page uses O(n) auxiliary space.
What topics does LeetCode 1424. Diagonal Traverse II cover?: LeetCode 1424. Diagonal Traverse II is tagged Array, Sorting and Heap (Priority Queue) on LeetCode.