Leetcode 中等：59. 螺旋矩阵II

题目：螺旋矩阵II

• 题号：59
• 难度：中等
• https://leetcode-cn.com/problems/spiral-matrix-ii/

给定一个正整数 n，生成一个包含 1 到 $n^2$ 所有元素，且元素按顺时针顺序螺旋排列的正方形矩阵。

示例1：

输入：n = 3
输出：[[1,2,3],[8,9,4],[7,6,5]]

示例 2：

输入：n = 1
输出：[[1]]

提示：

• 1 <= n <= 20

---

实现

C# 语言

public class Solution
{
    public int[][] GenerateMatrix(int n)
    {
        int[][] matrix = new int[n][];
        for (int i = 0; i < n; i++)
        {
            matrix[i] = new int[n];
        }

        int start = 0;//起始位置
        int end1 = n - 1;//最左边位置
        int end2 = n - 1;//最下边位置
        int count = 1;

        while (start < end1 && start < end2)
        {
            LeftToRight(start, end1, start, matrix, ref count);
            TopToBottom(start + 1, end2, end1, matrix, ref count);
            RightToLeft(end1 - 1, start, end2, matrix, ref count);
            BottomToTop(end2 - 1, start + 1, start, matrix, ref count);
            start++;
            end1 = n - 1 - start;
            end2 = n - 1 - start;
        }
        if (n%2 == 1)
        {
            matrix[start][start] = count;
        }
        return matrix;
    }

    private void LeftToRight(int start, int end, int rowIndex, int[][] matrix, ref int from)
    {
        for (int i = start; i <= end; i++)
        {
            matrix[rowIndex][i] = from;
            from++;
        }
    }

    private void TopToBottom(int start, int end, int colIndex, int[][] matrix, ref int from)
    {
        for (int i = start; i <= end; i++)
        {
            matrix[i][colIndex] = from;
            from++;
        }
    }

    private void RightToLeft(int start, int end, int rowIndex, int[][] matrix, ref int from)
    {
        for (int i = start; i >= end; i--)
        {
            matrix[rowIndex][i] = from;
            from++;
        }
    }

    private void BottomToTop(int start, int end, int colIndex, int[][] matrix, ref int from)
    {
        for (int i = start; i >= end; i--)
        {
            matrix[i][colIndex] = from;
            from++;
        }
    }
}

Python 语言

class Solution(object):
    def generateMatrix(self, n):
        """
        :type n: int
        :rtype: List[List[int]]
        """
        self.count = 1
        self.matrix = [[0 for i in range(n)] for i in range(n)]
        start, end1, end2 = 0, n - 1, n - 1
        while start < end1 and start < end2:
            self.LeftToRight(start, end1, start)
            self.TopToBottom(start + 1, end2, end1)
            self.RightToLeft(end1 - 1, start, end2)
            self.BottomToTop(end2 - 1, start + 1, start)
            start += 1
            end1 = n - 1 - start
            end2 = n - 1 - start
        if n % 2 == 1:
            self.matrix[start][start] = self.count
        return self.matrix

    def LeftToRight(self, start, end, rowIndex):
        for i in range(start, end + 1):
            self.matrix[rowIndex][i] = self.count
            self.count += 1

    def TopToBottom(self, start, end, colIndex):
        for i in range(start, end + 1):
            self.matrix[i][colIndex] = self.count
            self.count += 1

    def RightToLeft(self, start, end, rowIndex):
        for i in range(start, end - 1, -1):
            self.matrix[rowIndex][i] = self.count
            self.count += 1

    def BottomToTop(self, start, end, colIndex):
        for i in range(start, end - 1, -1):
            self.matrix[i][colIndex] = self.count
            self.count += 1