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 ]
]

public class Solution {
	public int[][] generateMatrix(int n) {
		int[][] res = new int[n][n];
		int cnt = 1;
		int top = 0;
		int bottom = n - 1;
		int left = 0;
		int right = n - 1;
		while (left < right && top < bottom) {
			for (int i = left; i < right; i++) {
				res[top][i] = cnt++;
			}
			for (int i = top; i < bottom; i++) {
				res[i][right] = cnt++;
			}
			for (int i = right; i > left; i--) {
				res[bottom][i] = cnt++;
			}
			for (int i = bottom; i > top; i--) {
				res[i][left] = cnt++;
			}
			left++;
			right--;
			top++;
			bottom--;
		}
		if (n % 2 != 0) {
			res[n/2][n/2] = cnt;
		}
		return res;
	}
}