Problem Overview & Intuition

Traverse in concentric rectangular layers. By keeping four boundaries (top, bottom, left, right), we traverse each edge in order and contract the boundary inwards until all elements are recorded.

Step-by-Step Approach

1. Set top = 0, bottom = m - 1, left = 0, right = n - 1.
2. Traverse left to right across top, then top++.
3. Traverse top to bottom down right, then right--.
4. If top <= bottom, traverse right to left across bottom, then bottom--.
5. If left <= right, traverse bottom to top up left, then left++.
6. Return accumulated result.

Optimal Implementation (JavaScript)

function spiralOrder(matrix) {
  if (!matrix.length) return [];
  const result = [];
  let top = 0, bottom = matrix.length - 1;
  let left = 0, right = matrix[0].length - 1;

  while (top <= bottom && left <= right) {
    for (let c = left; c <= right; c++) result.push(matrix[top][c]);
    top++;
    for (let r = top; r <= bottom; r++) result.push(matrix[r][right]);
    right--;
    if (top <= bottom) {
      for (let c = right; c >= left; c--) result.push(matrix[bottom][c]);
      bottom--;
    }
    if (left <= right) {
      for (let r = bottom; r >= top; r--) result.push(matrix[r][left]);
      left++;
    }
  }

  return result;
}

Complexity Analysis