Spiral Matrix Pathfinder

Given a 2D matrix where some cells contain obstacles (marked as -1), traverse the matrix in a spiral pattern starting from the top-left corner. Collect all non-obstacle values in the order they are visited.

Function Signature

function spiralMatrixPathfinder(matrix) {
  // Your code here
}

Parameters

• matrix: A 2D array where:
  • Regular cells contain integers (values to collect)
  • Obstacle cells contain -1 (to be avoided)

Return Value

• Return an array of integers representing the values collected in spiral order, excluding obstacles.

Examples

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

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

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

Spiral Pattern

The spiral traversal follows this pattern:

• Right: Top row from left to right
• Down: Right column from top to bottom
• Left: Bottom row from right to left
• Up: Left column from bottom to top
• Repeat, moving inward each time

Rules

• Obstacle Avoidance: Skip any cell with value -1
• Boundary Checking: Stay within matrix boundaries
• Visited Tracking: Don’t revisit already visited cells
• Spiral Direction: Always follow the spiral pattern (right → down → left → up)

Constraints

• (1 \leq \text{matrix.length} \leq 100)
• (1 \leq \text{matrix[i].length} \leq 100)
• All rows have the same length
• Matrix values are integers (including -1 for obstacles)
• Matrix is not empty

Algorithm

1. Use four pointers (top, bottom, left, right) to track the current boundaries.
2. Use a visited array to avoid revisiting cells.
3. Traverse in spiral order:
   • Right: Traverse the top row from left to right.
   • Down: Traverse the right column from top to bottom.
   • Left: Traverse the bottom row from right to left.
   • Up: Traverse the left column from bottom to top.
4. Collect non-obstacle values (value != -1) in traversal order.
5. Update boundaries after completing each direction.

Test Cases

• Regular matrices without obstacles
• Matrices with obstacles blocking paths
• Single row or single column matrices
• Empty matrices
• Matrices with all obstacles
• Edge cases with minimum size matrices