剑指offer之顺时针打印矩阵

问题：输入一个矩阵，按照从外向里以顺时针的顺序依次打印出每一个数字，例如，如果输入如下矩阵：1,2,3,4,5,6,7,8,9，则依次输出1,2,3,6,9,8,7,4,5

思路：利用循环，控制循环条件即可

具体代码如下：（C++）

class Solution

{

public:

    vector<int> printMatrix(vector<vector<int>> matrix)

    {

            int rows, columns;

            if(matrix.size() > 0)

            {

                    rows = matrix.size();

                    columns = matrix[0].size();

            }

            vector<int> res;    //由于保存结果

            int  startX = 0,  endX = columns -1;

            int  startY = 0,  endY = rows -1;

            while(startX <= endX && startY <= endY)

            {

                    if(startX <= endX && startY <= endY)

                    {

                            for(int i = startX; i<= endX; i++)

                                    res.push_back(matrix[startY][i]);    //上一行

                            ++startY;

                    }

                    if(startY <= endY  && startX <=endX)

                    {

                            for(int i = startY; i<=endY; i++)

                                    res.push_back(matrix[i][endX]);  //右一列

                            --endX;

                    }

                    if(startX <= endX && startY <= endY)

                    {

                            for(int i =endX; i>=startX; i--)

                                     res.push_back(matrix[endY][i]);  //下一行

                            --endY;

                    }

                    if(startY <= endY && startX <= endX)

                    {

                            for(int i=endY;i>= startY;i--)

                                    res.push_back(matrix[i][startX]);   //左一列

                            ++startX;

                    }

            }

            return res;

    }

};