JavaScriptMediumMatrices20 min
Traverse a matrix in spiral order
Return matrix values in clockwise spiral order, starting at the top-left corner. An empty matrix returns []. All input is valid JSON satisfying the constraints; do not mutate the meaning of values through type coercion. Interviewers use this problem to assess shrink four boundaries after traversing each outer edge.
Input
A JSON rectangular matrix of integers; [] is allowed.
Output
Print one compact JSON value: an array of integers.
Constraints
For nonempty matrices, 1 <= rows, columns <= 100; values between -1000000 and 1000000.
Example
Input
[[1,2,3],[4,5,6],[7,8,9]]
Output
[1,2,3,6,9,8,7,4,5]
Example 2 input
[[0,-1,2]]
Output
[0,-1,2]
Boundary case: Guard the bottom and left traversals to avoid revisiting a single row or column
Public test cases (2)
Input
[[1,2,3],[4,5,6],[7,8,9]]
Expected output
[1,2,3,6,9,8,7,4,5]
Input
[[1,2,3],[4,5,6]]
Expected output
[1,2,3,6,5,4]
Hints (2)
- Process top row, right column, bottom row, then left column
- Guard the bottom and left traversals to avoid revisiting a single row or column
Target complexity: time O(rows * columns) · space O(rows * columns)