59. 螺旋矩阵 II

mid

给你一个正整数 n ，生成一个包含 1 到 n2 所有元素，且元素按顺时针顺序螺旋排列的 n x n 正方形矩阵 matrix 。

1 <= n <= 20

模拟

就恩写；注意边界条件

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func generateMatrix(n int) [][]int {
	if n == 1 {
		return [][]int{{1}}
	}
	res := make([][]int, n)
	for i := 0; i < n; i++ {
		res[i] = make([]int, n)
	}
	count := 1
	for layer := 0; layer <= n-2; layer++ {
		// 顺时针填空 左闭右开 中心特例
		if layer == n-layer-1 {
			// 中心
			res[layer][layer] = n * n
			break
		}
		// l2r
		for col := layer; col < n-layer-1; col++ {
			res[layer][col] = count
			count++
		}
		// u2d
		for row := layer; row < n-layer-1; row++ {
			res[row][n-layer-1] = count
			count++
		}
		// r2l
		for col := n - layer - 1; col > layer; col-- {
			res[n-layer-1][col] = count
			count++
		}
		// d2u
		for row := n - layer - 1; row > layer; row-- {
			res[row][layer] = count
			count++
		}
	}
	return res
}

更好懂的模拟

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func generateMatrix(n int) [][]int {
    top, bottom := 0, n-1
    left, right := 0, n-1
    num := 1
    tar := n * n
    matrix := make([][]int, n)
    for i := 0; i < n; i++ {
        matrix[i] = make([]int, n)
    }
    for num <= tar {
        for i := left; i <= right; i++ {
            matrix[top][i] = num
            num++
        }
        top++
        for i := top; i <= bottom; i++ {
            matrix[i][right] = num
            num++
        }
        right--
        for i := right; i >= left; i-- {
            matrix[bottom][i] = num
            num++
        }
        bottom--
        for i := bottom; i >= top; i-- {
            matrix[i][left] = num
            num++
        }
        left++
    }
    return matrix
}