我的代码出现floating point exception错误，请求定位问题原因

Root Cause of Floating Point Exception #

Your program crashes with a floating-point exception because global variables are zero-initialized before main() runs. The global quantity starts at 0, so when target = rand() % quantity + 1 executes, you're performing rand() % 0—a division-by-zero operation that triggers the exception.

Key Issues & Fixes #

1. Global Variable Mismanagement #

• Global quantity, target, void_numbers, and points are initialized before user input, leading to invalid values (like division by zero).
• Local variables in main() shadow global ones, causing confusion and uninitialized variable usage (e.g., local quantity is used in rand() % quantity +1 before being assigned).
• Fix: Eliminate unnecessary global variables. Declare variables in main() or pass them as parameters to functions. Initialize all variables before use.

2. Undefined Variable invalidinput #

The loop while(invalidinput) references an undeclared variable, which is a compiler error.

• Fix: Replace with a boolean flag initialized to true, or restructure the loop to check input validity directly.

3. Broken Void Number Generation #

• The global unique flag isn't reset to true for each new number, so after the first duplicate, no more numbers are added to void_numbers.
• Generated void numbers aren't checked against target to ensure they're distinct.
• The duplicate removal loop has incorrect logic (erases elements improperly and fails to replace them with valid numbers).
• Fix: Use a std::unordered_set to track existing void numbers (automatically handles uniqueness). Reject any number equal to target when generating.

4. Poor Input Handling #

After clearing input errors, cin >> discard_value doesn't reliably consume invalid input.

• Fix: Use cin.ignore(numeric_limits<streamsize>::max(), '\n') to skip the entire line of invalid input.

Corrected Code #

#include <iostream>
#include <vector>
#include <cstdlib>
#include <string>
#include <ctime>
#include <unordered_set>
#include <limits>

using namespace std;

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

void generate_void_numbers(vector<int>& void_numbers, int quantity, int target) {
    unordered_set<int> used;
    while (used.size() < quantity) {
        int num = rand() % 20 + 1; // Target is between 1-20 per game rules
        if (num != target && used.find(num) == used.end()) {
            used.insert(num);
        }
    }
    void_numbers.assign(used.begin(), used.end());
}

void get_void_quantity(int& quantity) {
    cout << "How many void numbers would you like to add? (1-19): " << endl;
    while (true) {
        if (cin >> quantity && quantity >=1 && quantity <=19) {
            break;
        } else {
            cin.clear();
            cin.ignore(numeric_limits<streamsize>::max(), '\n');
            cout << "Invalid input. Please try again." << endl;
        }
    }
}

int main() {
    srand(time(0));
    int guesses = 3;
    int quantity;
    int target = rand() %20 +1; // Target is 1-20 per game rules
    vector<int> void_numbers;
    int points;

    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;

    get_void_quantity(quantity);
    generate_void_numbers(void_numbers, quantity, target);
    points = 10 + quantity *5;

    // Optional: Print void numbers for testing
    cout << "\nVoid numbers (for testing): ";
    for (int num : void_numbers) {
        cout << num << " ";
    }
    cout << "\nTarget (for testing): " << target << endl;

    // Game loop for guesses
    while (guesses >0) {
        int guess;
        cout << "\nEnter your guess: ";
        if (!(cin >> guess)) {
            cin.clear();
            cin.ignore(numeric_limits<streamsize>::max(), '\n');
            cout << "Invalid input. Please enter an integer." << endl;
            continue;
        }
        string result = check_guess(guess, void_numbers, target, guesses, points);
        cout << result << endl;
        if (result.find("win") != string::npos || result.find("lose") != string::npos) {
            break;
        }
    }

    return 0;
}

Additional Notes #

• The corrected code uses std::unordered_set to ensure void numbers are unique and not equal to the target.
• Input handling is improved to properly consume invalid input lines.
• Functions are modularized for better readability and maintainability.
• The full game loop is added to handle user guesses (missing in your original code).

内容的提问来源于stack exchange，提问作者doroyoki