面试题20：顺时针打印矩阵

比较复杂，见P128解析

void PrintMatrixClockwisely(int** numbers, int columns, int rows)
{
    if(numbers == NULL || columns <= 0 || rows <= 0)
        return;

    int start = 0;

    while(columns > start * 2 && rows > start * 2)
    {
        PrintMatrixInCircle(numbers, columns, rows, start);

        ++start;
    }
}

void PrintMatrixInCircle(int** numbers, int columns, int rows, int start)
{
    int endX = columns - 1 - start;
    int endY = rows - 1 - start;

    // 从左到右打印一行
    for(int i = start; i <= endX; ++i)
    {
        int number = numbers[start][i];
        printNumber(number);
    }

    // 从上到下打印一列
    if(start < endY)
    {
        for(int i = start + 1; i <= endY; ++i)
        {
            int number = numbers[i][endX];
            printNumber(number);
        }
    }

    // 从右到左打印一行
    if(start < endX && start < endY)
    {
        for(int i = endX - 1; i >= start; --i)
        {
            int number = numbers[endY][i];
            printNumber(number);
        }
    }

    // 从下到上打印一行
    if(start < endX && start < endY - 1)
    {
        for(int i = endY - 1; i >= start + 1; --i)
        {
            int number = numbers[i][start];
            printNumber(number);
        }
    }
}

 另一种方法：

http://blog.csdn.net/Irean_Lau/article/details/51072768

/*
    20 :> 顺时针打印数组
*/
vector<int> printMatrix(vector<vector<int> > matrix) {
    vector<int>res;
    res.clear();
    int row = matrix.size();//行数
    int col = matrix[0].size();//列数

    int circle = ((row < col ? row : col) - 1) / 2 + 1;//圈数

    for (int i = 0; i < circle; i++)
    {
        //zuo->you
        for (int j = i; j < col - i; ++j)
            res.push_back(matrix[i][j]);
        //shang->xia
        for (int k = i + 1; k < row - i; ++k)
            res.push_back(matrix[k][col - i - 1]);
        //you->zuo
        for (int l = col - i - 2; (l >= i) && (row - i - 1 != i); --l)
            res.push_back(matrix[row - i - 1][l]);
        //xia->shang
        for (int m = row - i - 2; (m > i) && (col - i - 1 != i); --m)
            res.push_back(matrix[m][i]);
    }
    return res;
}