【算法】顺时针打印矩阵

题目：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              10           11           12

13           14           15           16

则依次打印出数字1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 6, 7, 11, 10。

第一种思路：

代码转自网络，楼主整理了一下：

void printMatrixInCircle(int matrix[5][5],unsigned int nRow,unsigned int nCol)
{
    int upbound = 0, downbound = nRow - 1; int leftbound = 0, rightbound = nCol - 1; 
    enum direction {right,down,left,up}; 
    int row = 0, cloumn = 0; 
    direction dir = right;
    while ( 1 )
    {  
        cout << matrix [row][cloumn] << " "; 
        if  ( upbound == downbound && leftbound == rightbound)   
            break;
        switch ( dir ) {
        case right: 
            if ( cloumn < rightbound )
            {
                ++cloumn;
            } else if ( cloumn == rightbound )
            {
                ++upbound;
                ++row;
                dir = down;
            }
            break;
        case down:
            if ( row < downbound )
                ++row;
            else if ( row == downbound )
            {
                --rightbound;
                --cloumn;
                dir = left;
            }
            break;
        case left:
            if ( leftbound < cloumn )
                --cloumn;
            else if ( leftbound == cloumn )
            {
                --downbound;
                --row;
                dir = up;
            }
            break;
        case up:
            if ( row > upbound )
                --row;
            else if ( row == upbound ) 
            {
                ++leftbound;
                ++cloumn;
                dir = right;
            }
            break;
        }
    }
    cout << endl;
}

第二种思路：用递归：

思路是总打印第一行，然后创建新矩阵，新矩阵是把旧矩阵去掉第一行 然后逆时针旋转90度，递归

代码转自网络，楼主整理，部分修改：

void print( int** matrix, int num_of_rows, int num_of_cols)
{
    for( int col = 0; col < num_of_cols ; col++ )
    {
        cout << matrix[0][col] << " "; 
    }
    if( num_of_rows > 1 )
    {
     // using recursive function
     int newRows = num_of_cols ;
     int newCols = num_of_rows - 1;
     // create a new matrix
     int** newMatrix = new int*[newRows] ;

     for( int row = 0; row < newRows; row++ )
     {
           newMatrix[row]=new int[newCols];
     }
     for( int row = 0; row < newRows; row++ )
     {
           for( int col = 0; col < newCols; col++ )
           {
               newMatrix[row][col] = matrix[col+1][num_of_cols-row-1];
           }
     }
     print( newMatrix, newRows, newCols ) ;
     for( int row = 0; row < newRows; row++ )
     {
         delete [] newMatrix[row];
     }
     delete [] newMatrix;
    }

}

测试代码如下：

#include <iostream>
using namespace std;
void printMatrixInCircle(int matrix[5][5],unsigned int nRow,unsigned int nCol);
void print( int** matrix, int num_of_rows, int num_of_cols);
int main()
{ 
    int matrix[5][5] = {{1,2,3,4,5},{6,7,8,9,10},{11,12,13,14,15},{16,17,18,19,20},{21,22,23,24,25}}; 
    printMatrixInCircle(matrix,5,5);
    int **tmp = new int *[5];
    for (int i = 0; i != 5; ++i)
    {
        tmp[i] = new int[5];
    }
    for (int i = 0; i != 5; ++i)
    {
        for (int j = 0; j != 5;++j)
        {
            tmp[i][j] = i*5 + j + 1;
        }
    }
    print(tmp,5,5);
    for (int i = 0; i != 5; ++i)
    {
        delete []tmp[i];
    }
    delete []tmp;
    return 0;
}