題目：
輸入一個矩陣，按照從外向里以順時針的順序依次打印出每一個數字。

解法：

    void print(int a[4][3], int m, int n) {
        int mk = m/2 + m%2;
        int nk = n/2 + n%2;
        int c = mk > nk ? nk : mk;

        for (int k = 0; k < c; ++k) {
            for (int j = k; j < n-k; ++j) {
                cout << a[k][j] << "  ";
            }
            for (int i = k+1; i < m-k; ++i) {
                cout << a[i][n-1-k] << "  ";
            }
            for (int j = n-2-k; j >= k; --j) {
                cout << a[m-1-k][j] << "  ";
            }
            for (int i = m-2-k; i >= k+1; --i) {
                cout << a[i][k] << "  ";
            }
        }
    }