我的代码中出现的“浮点异常”错误在哪里？

Question

这里是学生程序员。每次我运行程序时，编译器都会终止并提示存在浮点异常。这是我的代码供参考：

#include <iostream>
#include <cmath>
#include <vector>
#include <cstdlib>
#include <string>
using namespace std;

int guesses = 3;
int quantity;
int discard_value;
vector<int> void_numbers(quantity);
int points = 10 + quantity * 5;
bool unique = 1;
int target = rand() % quantity + 1;

string check_guess(int guess)
{
  for (int i = 0; i < void_numbers.size(); i++)
    {
      if (guess == void_numbers[i])
        {
        return "You guessed a void number. You lose.";
        }
    }
  if (guess < target && guesses != 0)
  {
    return "Your guess is lower than the number.";
  }
  else if (guess > target && guesses != 0)
  {
    return "Your guess is higher than the number.";
  }
  else if (guess == target && guesses != 0)
  {
    return "You guessed the number. You win " + to_string(points) + " points.";
  }
  else if (guesses == 0)
  {
    return "You ran out of guesses. You lose.";
  }
  else
  {
    return "Invalid input. Please try again.";
  }
}


void test_input()
{
  cout << "How many void numbers would you like to add? (1-19): " << endl;
  while(invalidinput)
    {
      cin >> quantity;
      if (quantity < 1 || quantity > 19 || cin.fail())
      {
        cin.clear();
        cin.ignore();
        cin >> discard_value;
        cout << "Invalid input. Please try again." << endl;
      }
      else
      {
        break;
      }
    }
  while (void_numbers.size() < quantity)
    {
      int void_number = rand() % quantity + 1;
      for (int i = 0; i < void_numbers.size(); i++)
        {
          if (void_numbers[i] == void_number)
          {
            unique = 0;
            break;
          }

        }
      if (unique)
      {
        void_numbers.push_back(void_number);
      }
    }
  
  for (int i = 0; i < void_numbers.size(); i++)
    {
      for (int j = i + 1; j < void_numbers.size(); j++)
        {
          if (void_numbers[i] == void_numbers[j])
          {
            void_numbers.erase(void_numbers.begin() + j);
            j--;
            int temp_number = rand() % quantity + 1; 
            for (int i = void_numbers.size() - 1; i >= 0; i--)
              {
                if (void_numbers[i] == temp_number || void_numbers[i] == target)
                {
                  void_numbers.erase(void_numbers.begin() + j);
                }
              }
            }
          }
        }
  for (int i = 0; i < void_numbers.size(); i++)
    {
    cout << void_numbers[i] << endl; //currently have this here to test if the void numbers are being generated correctly
      cout << target;
    }
}
int main()
{
  srand(time(0));
  int quantity;
  int target = rand() % quantity + 1;
  char play;
  cout << "Welcome to the Numbers Game." << endl;
  cout << "1. In this game you have 3 guesses to guess a randomly-generated number between 1 and 20. The game will inform you if your guess is higher or lower than the random number." << endl;
  cout << "2. If you guess the number without running out of guesses, you receive 10 points. If you want more points, you have the option of inputting a quantity of void numbers." << endl;
  cout << "3. Void numbers make you instantly lose the game if you guess one of them, but each additional void number adds 5 additional points to your total score." << endl;
  cout << "4. If you use all your guesses and don't guess the number, you lose the game." << endl;
  test_input();
}

整个程序是一个用户猜数字的游戏。在游戏开始之前，用户可以输入一定数量的无效数字，如果猜中其中一个数字，则用户将输掉游戏。 test_input 函数应该用于在向量中生成从 1 到用户想要的任何数量（最多 19）的数字，而无需任何重复数字。向量中的数字也不应该与目标变量中存储的数字匹配。

Answer 1

真的要避免全局变量。

int quantity;

这是一个没有初始化器的变量定义。当它出现在块作用域时，它的值将是不确定的。相反，这里我们将它放在文件范围内，并且它是一个全局变量，其值初始化为零。

int target = rand() % quantity + 1;

这通过计算

target

来初始化另一个全局变量

rand() % quantity +1

。由于

quantity

为零，因此除以零，这是未定义的行为，任何事情都可能发生。在您的特定情况下，它可能会导致除零浮点异常信号，但这不能保证。