0059.螺旋矩阵 II

https://leetcode.cn/problems/spiral-matrix-ii/

方法一：模拟

时间复杂度 $O(n^2)$，空间复杂度 $O(1)$。

func generateMatrix(n int) [][]int {
	ans := make([][]int, n)
	for i := 0; i < n; i++ {
		ans[i] = make([]int, n)
	}
	top, bottom, left, right, v := 0, n-1, 0, n-1, 1
	for top <= bottom && left <= right {
		for i := left; i <= right; i++ {
			ans[top][i], v = v, v+1
		}
		top += 1
		for i := top; i <= bottom; i++ {
			ans[i][right], v = v, v+1
		}
		right -= 1
		if top > bottom || left > right {
			break
		}
		for i := right; i >= left; i-- {
			ans[bottom][i], v = v, v+1
		}
		bottom -= 1
		for i := bottom; i >= top; i-- {
			ans[i][left], v = v, v+1
		}
		left += 1
	}
	return ans
}