54. Spiral Matrix

螺旋式遍历矩阵
如下图所示的方法。

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

For example,
Given the following matrix:

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

You should return [1,2,3,6,9,8,7,4,5].

思路

递归实现

code

 public class Solution    {        private IList<int> rtn = new List<int>();        public IList<int> SpiralOrder(int[,] matrix)        {            int m = matrix.GetUpperBound(0); //row index upper bound            int n = matrix.GetUpperBound(1); //            spiral(matrix, 0, n, m, 0);            return rtn;        }        public void spiral(int[,] matrix, int top, int right, int bottom, int left)        {            if (top > bottom || left > right) return;            //add first row            for (int j = left; j <= right; j++)                rtn.Add(matrix[top, j]);            //add last column            for (int i = top + 1; i <= bottom; i++)                rtn.Add(matrix[i, right]);            //add last row            for (int j = right - 1; j >= left && top!=bottom; j--)                rtn.Add(matrix[bottom, j]);            //add first column            for (int i = bottom - 1; i > top && left!=right; i--)                rtn.Add(matrix[i, left]);            spiral(matrix, top + 1, right - 1, bottom - 1, left + 1);        }    }