用c++写Write a program which reads two integers x and y, and prints them in ascending order. 输入 The input consists of multiple datasets. Each dataset consists of two integers x and y separated by a single space. The input ends with two 0 (when both x and y are zero). Your program should not process for these terminal symbols. 输出 For each dataset, print x and y in ascending order in a line. Put a single space between x and y.

以下是用 C++ 编写的程序：

#include <iostream>
using namespace std;

int main() {
    int x, y;
    while (cin >> x >> y) {
        if (x == 0 && y == 0) break;  // 终止条件
        if (x > y) swap(x, y);       // 交换 x 和 y
        cout << x << " " << y << endl;
    }
    return 0;
}

程序的逻辑很简单，就是读入两个整数 x 和 y，然后比较它们的大小，将它们按升序输出。当输入的 x 和 y 均为 0 时，程序结束。