斐波那契数列对大数出错 我刚刚开始学习C++，这里是我的C++代码，用来生成斐波那契序列。p> #include <iostream> using namespace std; int main() { int n; while(true){ cout << "Enter the number of terms upto which a the fibonocci sequence should be generated: "; cin >> n; cout << "------------------------" << endl; long long fib1 = 1; long long fib2 = 1; long long fibnext; cout << 1 << " " << fib1 << endl << 2 << " " << fib2 <<endl; for (int i =1; i <= n-2; ++i){ fibnext = fib1 + fib2; fib1 = fib2; fib2 = fibnext; cout << i+2 << " " << fibnext << endl; } } return 0; }

请查看下表中的值：

4660046610375530309 - 92nd Fibonacci number 9223372036854775807 - largest 64-bit two's complement, 2^63 - 1 12200160415121876738 - 93rd Fibonacci number 18446744073709551615 - largest 64-bit unsigned, 2^64 - 1 对于较大的值，可以切换到任意精度（通俗地称为“bignum”）数学库，例如

---

作为示例，以下是修改后的原始代码，以使用MPIR并输出前千个斐波那契数：

#include <mpir.h>
#include <iostream>

// Helper function for checked output.

void OutZ(int num, mpz_t &x) {
    static char textX[10000]; // can handle up to fib(47846)
    if (gmp_snprintf(textX, sizeof(textX), "%Zd", x) >= sizeof(textX)) {
        std::cout << "*** ERROR: Number was too big, need more space\n";
        exit(1);
    }
    std::cout << num << " " << textX << '\n';
}

int main() {
    // Initialise all MPIR integers to specific values.

    mpz_t fib1, fib2, fib3;

    mpz_init_set_ui(fib1, 1);          // fib1 = 1
    mpz_init_set_ui(fib2, 1);          // fib2 = 1
    mpz_init(fib3);                    // fib3 = 0

    // No need for helper, these first two are well-known.

    std::cout << "1 1\n2 1\n";

    // Now do the rest of them.

    for (int i = 3; i <= 1000; ++i) {
        mpz_add(fib3, fib1, fib2);     // fib3 = fib1 + fib2
        mpz_set(fib1, fib2);           // fib1 = fib2
        mpz_set(fib2, fib3);           // fib2 = fib3

        OutZ(i, fib3);
    }

    return 0;
}

您可以通过询问以下问题来验证最终结果：

---

请查看下表中的值：

4660046610375530309 - 92nd Fibonacci number 9223372036854775807 - largest 64-bit two's complement, 2^63 - 1 12200160415121876738 - 93rd Fibonacci number 18446744073709551615 - largest 64-bit unsigned, 2^64 - 1 对于较大的值，可以切换到任意精度（通俗地称为“bignum”）数学库，例如

---

作为示例，以下是修改后的原始代码，以使用MPIR并输出前千个斐波那契数：

#include <mpir.h>
#include <iostream>

// Helper function for checked output.

void OutZ(int num, mpz_t &x) {
    static char textX[10000]; // can handle up to fib(47846)
    if (gmp_snprintf(textX, sizeof(textX), "%Zd", x) >= sizeof(textX)) {
        std::cout << "*** ERROR: Number was too big, need more space\n";
        exit(1);
    }
    std::cout << num << " " << textX << '\n';
}

int main() {
    // Initialise all MPIR integers to specific values.

    mpz_t fib1, fib2, fib3;

    mpz_init_set_ui(fib1, 1);          // fib1 = 1
    mpz_init_set_ui(fib2, 1);          // fib2 = 1
    mpz_init(fib3);                    // fib3 = 0

    // No need for helper, these first two are well-known.

    std::cout << "1 1\n2 1\n";

    // Now do the rest of them.

    for (int i = 3; i <= 1000; ++i) {
        mpz_add(fib3, fib1, fib2);     // fib3 = fib1 + fib2
        mpz_set(fib1, fib2);           // fib1 = fib2
        mpz_set(fib2, fib3);           // fib2 = fib3

        OutZ(i, fib3);
    }

    return 0;
}

您可以通过询问以下问题来验证最终结果：

---

这是因为原始整数类型的精度是有限的

long-long

保证至少有64位，但通常不再有。您需要使用某种类型的bignum/bigint实现（最好是一个已经存在的库），以获得无限（而不是任意）精度？您的变量很可能溢出，因为第93个斐波那契数非常大]使用任意精度的数学库：第93个斐波那契数是最大的一个，适合64位，但它需要一个无符号类型。谢谢，我看到了这个GMP库，我将在以后使用它，因为基本整数类型的精度是有限的

long-long

保证至少有64位，但通常不再有。您需要使用某种类型的bignum/bigint实现（最好是一个已经存在的库），以获得无限（而不是任意）精度？您的变量很可能溢出，因为第93个fibonacci数非常大]使用任意精度的数学库：第93个fibonacci数是适合64位的最大数，但它需要一个无符号类型。谢谢，我看到了这个GMP库，稍后我将使用它

999 26863810024485359386146727202142923967616609318986952340123175997617981700247881689338369654483356564191827856161443356312976673642210350324634850410377680367334151172899169723197082763985615764450078474174626
1000 43466557686937456435688527675040625802564660517371780402481729089536555417949051890403879840079255169295922593080322634775209689623239873322471161642996440906533187938298969649928516003704476137795166849228875

Result:
43466557686937456435688527675040625802564660517371780402481729089536555417949051890403879840079255169295922593080322634775209689623239873322471161642996440906533187938298969649928516003704476137795166849228875