LeetCode实战：螺旋矩阵 II

题目英文

Given a positive integer n, generate a square matrix filled with elements from 1 to n^2 in spiral order.

Example:

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

题目中文

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:

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

算法实现

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++;}}}