C ++中的斐波那契数列不能超过47个数字 [英] Fibonacci series in C++ can't get more than 47 numbers

问题描述

我设计了这个程序，可以打印斐波那契数列( series [i] = series [i-1] + series [i-2] )，但我得到的数字不能超过47因为第48个数字变为负数和奇数(我认为这是在列表超出范围或该项为null时发生的情况):

I designed this program that can print the Fibonacci Series (series[i] = series[i-1] + series[i-2]) but i can't get more than 47 numbers because the 48th they become negative and strange numbers (i think this happens when the list is out of range or the item is null):

#include <iostream>
#include <vector>

using namespace std;

int main ()
{
    int length;
    string again = "";
    do {
        cout << "Enter the length you want in your sequence: ";
        cin >> length;
        vector<int> series(length);
        for (int n=0; n<=1; n++) series[n] = n;
        for (int number=2; number<=length; number++) {
            series[number] = series[number-1] + series[number-2];
        }
        for (int i=0; i<length; i++) cout << series[i] << " ";
        cout << endl << "Do it again ? <y/n> ";
        cin >> again;
        cout << endl;
    } while (again == "y");
}

改进"的代码:

#include <iostream>
#include <vector>
#include <string>

std::vector<int> fibonacci (int length)
{
    std::vector<int> series(length);
    series[0] = 0;
    series[1] = 1;
    for (int num=2; num<length; num++) {
        series[num] = series[num-1] + series[num-2];
    }
    return series;
}

int main ()
{
    std::string again;
    do {
        std::cout << "Enter how many numbers you want in your series: ";
        int length;
        std::cin >> length;
        std::vector<int> series(length);
        series = fibonacci(length);
        for (int n=0; n<length; n++) std::cout << series[n] << " ";
        std::cout << "\nDo it again <y/n> ? ";
        std::cin >> again;
        std::cout << std::endl;
    } while (again == "y");
}

推荐答案

当获得第47个值时，数字超出 int 范围. int 的最大值为 2,147,483,647 ，第46个数字位于 1,836,311,903 的正下方.第47个数字超过了最大值， 2,971,215,073 .

When you get to the 47th value, the numbers go out of int range. The maximum int value is 2,147,483,647 and the 46th number is just below at 1,836,311,903. The 47th number exceeds the maximum with 2,971,215,073.

此外，正如LeonardBlunderbuss提到的那样，您使用的 for 循环超出了向量的范围.向量以 0 开头，因此通过具有 number< = length; ，将调用 range + 1 元素.范围只能达到 length-1 .

Also, as LeonardBlunderbuss mentioned, you are exceeding the range of the vector with the for loop that you have. Vectors start with 0, and so by having number<=length; the range+1 element will be called. The range only goes up to length-1.

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