Is Diagonal Traverse easy or hard?

Diagonal Traverse is considered a medium-level problem. The main challenge comes from correctly handling edge cases when the traversal hits matrix borders and ensuring the direction switches at the right time.

How to solve Diagonal Traverse in O(n)?

The optimal solution runs in O(m*n) because all matrix elements must be processed. Use a simulation approach that moves diagonally and flips direction when hitting matrix boundaries. Another method groups elements by the key row+col and then processes diagonals with alternating order.

What is the best approach for Diagonal Traverse?

Direct simulation is the most common approach. It tracks the current direction (up-right or down-left) and switches direction whenever a matrix boundary is reached. The algorithm visits each element once, giving O(m*n) time and O(1) extra space, which makes it efficient and interview-friendly.

What data structure is used in Diagonal Traverse?

The simulation approach mainly uses arrays and index variables. The alternative grouping method uses a hash map or array of lists keyed by row+col to store elements belonging to the same diagonal before constructing the final traversal order.

What is the time complexity of Diagonal Traverse?

The time complexity is O(m*n) where m is the number of rows and n is the number of columns. Every matrix element is visited exactly once during the traversal. Space complexity is O(1) for the simulation method or O(m+n) if diagonals are stored in a hash map.

Diagonal Traverse Python or Java solution approach?

Both Python and Java implementations typically follow the direct simulation pattern. Maintain row, column, and direction variables, append elements to the result, and adjust direction when hitting matrix edges. The algorithm remains O(m*n) with constant extra space.

Is Diagonal Traverse asked at Google, Amazon, or Meta?

Matrix traversal problems like Diagonal Traverse frequently appear in interviews at companies such as Amazon, Google, and Meta. They test boundary handling, index manipulation, and understanding of matrix patterns rather than advanced data structures.

Description Solution Video 6:56

498. Diagonal Traverse

Medium67.1% acceptance12 companies

Given an m x n matrix mat, return an array of all the elements of the array in a diagonal order.

Example 1:

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

Example 2:

Input: mat = [[1,2],[3,4]]
Output: [1,2,3,4]

Constraints:

m == mat.length
n == mat[i].length
1 <= m, n <= 10⁴
1 <= m * n <= 10⁴
-10⁵ <= mat[i][j] <= 10⁵

Asked at 12 companies

Nike Liftoff Meta Oracle Walmart Labs

Cisco Zoho

Google Amazon Microsoft Bloomberg Tiktok

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6:56

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498. Diagonal Traverse

Asked at 12 companies

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