c++ - C++长整数奇数？

在熟悉C ++的过程中，我正在重新研究一些初学者的算法。我已经不知道从哪里开始修复了一些错误。

1）以下是在fib()函数返回其结果时出现的段错误。编辑：输入> = 9

#include <iostream>

using namespace std;

int fib(int n) {
    int fibs[] = {1, 1};    // dynamic array
    int i = 2;              // start at 3rd element
    while(i < n) {
        fibs[i] = fibs[i-2] + fibs[i-1];
        cout << "DEBUG: fibs[" << i << "] = " << fibs[i] << endl;
        i = i+1;
    }
    cout << "about to return to main()" << endl;
    return fibs[n-1];
}

int main() {
    cout << "\n================= Hello cruel world =================" << endl;
    cout << "Enter a number:  ";
    int x;
    cin >> x;
    cout << "fib(" << x << ") = " << fib(x) << endl;
    cout << "================ Goodbye cruel world ================\n" << endl;
    return 0;
}

否则，代码工作正常，可以正确找到数字。但是2）当我更改函数以支持长整数时，它开始表现得很奇怪：

#include <iostream>

using namespace std;

long fib(int n) {
    long fibs[] = {1L, 1L};    // dynamic array
    int i = 2;                 // start at 3rd element
    while(i < n) {
        fibs[i] = fibs[i-2] + fibs[i-1];
        cout << "DEBUG: fibs[" << i << "] = " << fibs[i] << endl;
        i = i+1;
    }
    cout << "about to return to main()" << endl;
    return fibs[n-1];
}

int main() {
    cout << "\n================= Hello cruel world =================" << endl;
    cout << "Enter a number:  ";
    int x;
    cin >> x;
    cout << "fib(" << x << ") = " << fib(x) << endl;
    cout << "================ Goodbye cruel world ================\n" << endl;
    return 0;
}

输出：

================= Hello cruel world =================
Enter a number:  7
DEBUG: fibs[2] = 2
DEBUG: fibs[0] = 1
DEBUG: fibs[1] = 30071067265
DEBUG: fibs[2] = 30071067266
DEBUG: fibs[14] = 0
about to return to main()
fib(7) = 140733637791872
================ Goodbye cruel world ================

这对我来说没有任何意义。谢谢你的帮助。

最佳答案

int fibs[] = {1, 1};

等效于：

int fibs[2] = {1, 1};

换句话说，数组fibs（在两个程序中）只有两个元素，如果fibs[n]大于n，则访问1是非法的。

关于c++ - C++长整数奇数？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/20866205/