Spiral Matrix

Traverse a 2D matrix in spiral order starting from the top-left corner.

Code

Algorithms

const result = [];
let top = 0, bottom = matrix.length - 1, left = 0, right = matrix[0].length - 1;
while (top <= bottom && left <= right) {
  for (let i = left; i <= right; i++) result.push(matrix[top][i]);
  top++;
  for (let i = top; i <= bottom; i++) result.push(matrix[i][right]);
  right--;
  if (top <= bottom) { for (let i = right; i >= left; i--) result.push(matrix[bottom][i]); bottom--; }
  if (left <= right) { for (let i = bottom; i >= top; i--) result.push(matrix[i][left]); left++; }
}
return result;

Parameters

matrix(array)

2D matrix

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