while 循环的结尾非常有问题显示不正确的迭代

如何解决while 循环的结尾非常有问题显示不正确的迭代

#include <iostream>
#include <ctime>
#include <string>

using namespace std;

int main()
{
    time_t program_time;
    time(&program_time);   //Time variable displays time

    string name;    //name variable,displays the name enter into cin

    int a;
    int b;
    int c;

    cout << "This is a C++ version of the Euclidean algorithm\n";
    cout << "it is named after the Greek mathematician Euclid.\n";
    cout << "What is your first name?\n";

    cin >> name;

    cout << "Hello "<< name <<",Please enter two numbers.\n";
    cout << "Entry (1): "<< endl;

    cin >> a;

    cout << "You entered: " << a << endl;
    cout << "Entry (2): " << endl;

    cin >> b;

    cout << "You entered: " << b << endl;

    if(a < b) { //swaps entries
       c = a;
       a = b;
       b = c;
    }

    while(a != b) {//control
        int z = a;
        do {
            if(a != 1 && (!(a < b))) {
                cout << "\n" << a << " minus "; //displays calculation
            }
            if(a < b) {
                b -= a;
            } else {
                a -= b;
            }
            if(a != 1 && (!(a < b))) {
                cout << b << " equals:\n" << "   " << a << endl;  //displays result of each calculation
            }
        } while(a < b);
        if(a == 1) {
            cout << "   " << a << endl;
        }
    }

    cout << "\n" << name << ",this is the greatest common divisor: " << a << endl;
    cout << "\nWould you like to know the time?(yes/no) if not,this program is complete (case sensitive).\t";
    string yes = "yes";

    cin >> yes;

    if(yes == "yes") {
        cout << ctime(&program_time) << endl;  //displays time
        cout << "Good Bye!";
    } else {
        cout << "Good Bye!";
    }
    return 0;
}

例如，如果我输入 234 和 23 那么这就是最终输出显示的内容：

50 minus 23 equals:
   27

27 minus 3 equals:
   4

4 minus    1

stackoverflow,this is the greatest common divisor: 1

我无法弄清楚，我已经研究了几个小时。

我需要包括每次迭代的计算和结果。如果有更简单的方法来做到这一点，我会很感激并对其进行更改，但我希望有一些建议不会彻底改变我的程序

解决方法

你让这件事变得比你需要的要复杂得多。 Euclid 的算法完全是关于减法，并在结果为负时翻转顺序。下面演示了一个非常精简的版本：

#include <iostream>
#include <ctime>
#include <string>

int main()
{
    unsigned int a,b;
    if (std::cin >> a >> b && a > 0 && b > 0)
    {
        while (a != b && a > 1 && b > 1)
        {
            if (b < a)
            {
                std::cout << a << " - " << b << " = ";
                a -= b;
                std::cout << a << '\n';
            }
            else
            {
                std::cout << b << " - " << a << " = ";
                b -= a;
                std::cout << b << '\n';
            }
        }
        std::cout << "Ans: " << a << '\n';
    }
    return 0;
}

一些事情。我们读取无符号整数（所以......没有负输入）。其次，不要费心在循环之前检测两者中的较大者；没关系。代码已经通过反转减法的参数来说明这一点。事实上，这就是算法的指针。输入测试值为 234 23 的示例运行：

样本（第一行是输入）

234
23
234 - 23 = 211
211 - 23 = 188
188 - 23 = 165
165 - 23 = 142
142 - 23 = 119
119 - 23 = 96
96 - 23 = 73
73 - 23 = 50
50 - 23 = 27
27 - 23 = 4
23 - 4 = 19
19 - 4 = 15
15 - 4 = 11
11 - 4 = 7
7 - 4 = 3
4 - 3 = 1

---

参考替代

您可以通过初始化对 a 和 b 的两个引用来进一步压缩它，较大的绑定到 lhs 引用，较小的绑定到 rhs 引用。从图形上看，它是有道理的，并且具有将代码减少到仅一个减法和报告部分的好处：

#include <iostream>

int main()
{
    unsigned int a,b;
    if (std::cin >> a >> b && a > 0 && b > 0)
    {
        while (a != b && a > 1 && b > 1)
        {
            unsigned int &lhs = (a < b) ? b : a;
            unsigned int &rhs = (a < b) ? a : b;

            std::cout << lhs << " - " << rhs << " = ";
            lhs -= rhs;
            std::cout << lhs << '\n';
        }
        std::cout << "Ans: " << a << '\n';
    }
    return 0;
}

,

关于信息的错误显示，以下代码是错误的，因为您正在减少值，然后进行与上述相同的检查。在某些时候（当 b 大于 a 时），您将开始跳过 'cout

if(a != 1 && (!(a < b))) {
            cout << "\n" << a << " minus "; //displays calculation
        }
        if(a < b) {
            b -= a;
        } else {
            a -= b;
        }
        if(a != 1 && (!(a < b))) {
            cout << b << " equals:\n" << "   " << a << endl;  //displays result of each calculation
        }

这里有一个小解决方案

if(a != 1 && (!(a < b))) {
            cout << "\n" << a << " minus " << b << " equals:\n" << "   " << a-b << endl;; //displays calculation
        }
        else
        if(a != 1 && (a < b))
        {
          cout << "\n" << b << " minus " << a << " equals:\n" << "   " << b-a << endl;; //displays calculation
        }
        if(a < b) {
            b -= a;
        } else {
            a -= b;
        }