Spiral Matrix II

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

For example,

Given n = 3,

You should return the following matrix:

[ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ]

Solution:

public int[][] generateMatrix(int n) { int[][] result = new int[n][n]; if (n == 0) { return result; } int rowBegin = 0; int rowEnd = n - 1; int colBegin = 0; int colEnd = n - 1; int i = 1; while (rowBegin <= rowEnd && colBegin <= colEnd) { for (int j = colBegin; j <= colEnd; j++) { result[rowBegin][j] = i++; } rowBegin++; for (int j = rowBegin; j <= rowEnd; j++) { result[j][colEnd] = i++; } colEnd--; if (rowBegin <= rowEnd) { for (int j = colEnd; j >= colBegin; j--) { result[rowEnd][j] = i++; } } rowEnd--; if (colBegin <= colEnd) { for (int j = rowEnd; j >= rowBegin; j--) { result[j][colBegin] = i++; } } colBegin++; } return result; }