59. Spiral Matrix II

题目

生成螺旋矩阵
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 ]]

思路

递归实现

code

public class Solution {        private int[,] matrix;        private int elen;        public int[,] GenerateMatrix(int n)        {            matrix = new int[n, n];            elen = 0; //element count            spiral(0, n-1, n-1, 0);            return matrix;        }        private void spiral(int top, int right, int bottom, int left)        {            if (top > bottom || left > right) return;            //add first row            for (int j = left; j <= right; j++)                matrix[top, j] = ++elen;            //add last column            for (int i = top + 1; i <= bottom; i++)                matrix[i, right] = ++elen;            //add last row            for (int j = right - 1; j >= left && top != bottom; j--)                matrix[bottom, j] = ++elen;            //add first column            for (int i = bottom - 1; i > top && left != right; i--)                matrix[i, left] = ++elen;            spiral(top + 1, right - 1, bottom - 1, left + 1);        }}