Spiral Matrix

LeetCode

LeetCode: https://leetcode.com/problems/spiral-matrix/

Given an m x n matrix, return all elements of the matrix in spiral order.

Example 1:

Spiral Matrix 1

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

Example 2:

Spiral Matrix 2

  • Input: matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]
  • Output: [1,2,3,4,8,12,11,10,9,5,6,7]
1def spiralOrder(matrix: List[List[int]]) -> List[int]:
2    if not matrix: return []
3    res = []
4    top, bottom = 0, len(matrix) - 1
5    left, right = 0, len(matrix[0]) - 1
6    
7    while top <= bottom and left <= right:
8        # Traverse Right
9        for i in range(left, right + 1):
10            res.append(matrix[top][i])
11        top += 1
12        
13        # Traverse Down
14        for i in range(top, bottom + 1):
15            res.append(matrix[i][right])
16        right -= 1
17        
18        if top <= bottom:
19            # Traverse Left
20            for i in range(right, left - 1, -1):
21                res.append(matrix[bottom][i])
22            bottom -= 1
23            
24        if left <= right:
25            # Traverse Up
26            for i in range(bottom, top - 1, -1):
27                res.append(matrix[i][left])
28            left += 1
29            
30    return res
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Spiral Order (From Center)
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Spiral Matrix II
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top=0
bottom=2
left=0
right=2
result=[]
Step 1 / 6
Step 1:
Initialize boundaries: top=0, bottom=2, left=0, right=2.
Focus: default
top=0bottom=2left=0right=2