c++ - 元素 vector 加法表现怪异

Question

在进入问题描述之前，请注意数据类型“factrep”只是 vector<int> 的类型定义。 .

问题

给定两个 factrep对象 f1 & f2 , 作为参数传递给 factrep函数 mult ，我希望返回 factrep对象 result成为相乘 vector 的表示。

另请注意，对 vector 的元素单独执行的实际算术运算是加法:这是因为 vector 以素数指数的形式存储(元素 0 = 素数 2 的幂) , 元素 1 = 质数 3 的次方存储量)。因此，这样添加元素应该是正确的，但我的结果并不连贯。我会将结果发布在附录中。

这里是相关函数

factrep mult(factrep f1, factrep f2)
{
    factrep a;

    for(unsigned int i=0;  i <f1.size() && f2.size(); i++) a.push_back(0);

    for(int i = 0; i < a.size(); i++)
    {
        a[i] += f1[i]+f2[i];
    }

    return a;
}

这里是完整的代码，包括调试控制台输出

#include "facth_new.h"
#include <iostream>
#include <cmath>
#include <climits>
#include <vector>

using namespace std;

std::vector<int> eratosthenes(int n) {
    std::vector<int> result = std::vector<int>();
    if (n < 2) {
        return result;
    }

    // initialize the vector
    std::vector<bool> input(n + 1, true);

    // calculate the upper limit as the square root of
    // of N. all composite numbers <= N must have a
    // factor <= sqrt(N)
    int sqrtN = (int)sqrt(n);

    // iterate from 2 up to the square root of N
    for (int i = 2; i <= sqrtN; i ++) {
        if (! input[i]) {
            // i is a proven composite number,
            // all its multiples have been
            // marked not prime by all its prime factors by now.
            continue;
        }

        // as an optimization, all multiples *less* than
        // the square of i are already marked, (they have
        // another prime factor less than i), so we can start
        // from the square which is the smallest composite
        // not yet marked
        for (int j = i * i; j <= n; j += i) {
            input[j] = false;
        }
    }

    // as n >= 2, then add 2 here
    result.push_back(2);

    // and check only odd numbers here,
    // no other even number can be set
    for (int i = 3; i <= n; i += 2) {
        if (input[i]) {
            result.push_back(i);
        }
    }

    return result;
}


factrep primfact(int n){
    factrep a;

    int m; // still to factorize number

    m=n;

    // continue until nothing to factorize
    for(int i = 0; m != 1; i++)
    {
        a.push_back(0);
        while(m % primes[i] == 0){

            m=m/primes[i];
            a.at(i)++;

        }

    }

    return a;
}

factrep mult(factrep f1, factrep f2)
{
    factrep a;

    for(unsigned int i=0;  i <f1.size() && f2.size(); i++) a.push_back(0);

    for(int i = 0; i < a.size(); i++)
    {
        a[i] += f1[i]+f2[i];
    }

    return a;
}

factrep div(factrep f1, factrep f2)
{
    factrep result;

    for(int i=0; i<f1.size(); i++){
        result.push_back(f1[i]-f2[i]);
    }

    return result;
}

double getval(factrep f)
{
    double result = 1;

    for(unsigned int i = 0; i < f.size(); i++)
    {

        result *= pow(primes[i],f[i]);

    }

    return result;
}

vector<int> primes;

int main() {

    primes = eratosthenes(71);
    cout << "The prime numbers are:\n";

    for(unsigned i = 0; i != primes.size(); i++)
        cout << primes[i] << '\n';

    int num[] = {1, 17, 54, 10, 36, 63, 20, 25};
    factrep f[8];


    for(int i = 0; i != 8; i++) {
        f[i] = primfact(num[i]);
    }

    for(int i = 0; i != 8; i++) {
        cout << '\n' << num[i] << " is factorized as:\nPrime     Exponent\n";
        bool agree = true;
        for(unsigned j = f[i].size(); j < f[i].size(); j++) {
            if((f[i])[j] != 0) {
                agree = false;
            }
        }
        for(unsigned j = 0; j != min(f[i].size(), f[i].size()); j++) {
            if((f[i])[j] != 0) {
                cout << primes[j] << "     " << (f[i])[j] << '\n';
            }
        }
        if(!agree) {
            for(unsigned j = f[i].size(); j != f[i].size(); j++) {
                if((f[i])[j] != 0) {
                    cout << primes[j] << "     " << (f[i])[j] << '\n';
                }
            }
        }
    }

    for(int i = 0; i != 8; i++) {
        cout << "getval of " << num[i] << " is " << getval(f[i]) << "\n\n";
    }

    for(int i = 0; i != 8; i++) {
        for(int j = i; j != 8; j++) {
            factrep res = mult(f[i], f[j]);
            cout << num[i] << " multiplied by " << num[j] << " is " << getval(res) << "\n";
        }
    }
    for(int i = 0; i != 8; i++) {
        for(int j = i; j != 8; j++) {
            factrep res = div(f[i], f[j]);
            cout << num[i] << " divided by " << num[j] << " is " << getval(res) << "\n";
        }
    }

}

最后，我的调试控制台打印出乘法部分出现的错误:

The prime numbers are:
2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71

1 is factorized as:
Prime     Exponent

17 is factorized as:
Prime     Exponent
17     1

54 is factorized as:
Prime     Exponent
2     1
3     3

10 is factorized as:
Prime     Exponent
2     1
5     1

36 is factorized as:
Prime     Exponent
2     2
3     2

63 is factorized as:
Prime     Exponent
3     2
7     1

20 is factorized as:
Prime     Exponent
2     2
5     1

25 is factorized as:
Prime     Exponent
5     2
getval of 1 is 1

getval of 17 is 17

getval of 54 is 54

getval of 10 is 10

getval of 36 is 36

getval of 63 is 63

getval of 20 is 20

getval of 25 is 25

1 multiplied by 1 is 1
1 multiplied by 17 is 1
1 multiplied by 54 is 1
1 multiplied by 10 is 1
1 multiplied by 36 is 1
1 multiplied by 63 is 1
1 multiplied by 20 is 1
1 multiplied by 25 is 1
17 multiplied by 17 is 289
17 multiplied by 54 is 9.12788e+172
17 multiplied by 10 is 1.69035e+172
17 multiplied by 36 is 3.04263e+173
17 multiplied by 63 is 1.06492e+173
17 multiplied by 20 is 2.36649e+173
17 multiplied by 25 is 2.95811e+173
54 multiplied by 54 is 2916
54 multiplied by 10 is 108
54 multiplied by 36 is 1944
54 multiplied by 63 is 486
54 multiplied by 20 is 216
54 multiplied by 25 is 54
10 multiplied by 10 is 100
10 multiplied by 36 is 9000
10 multiplied by 63 is 90
10 multiplied by 20 is 200
10 multiplied by 25 is 250
36 multiplied by 36 is 1296
36 multiplied by 63 is 324
36 multiplied by 20 is 144
36 multiplied by 25 is 36
63 multiplied by 63 is 3969
63 multiplied by 20 is 61740
63 multiplied by 25 is 540225
20 multiplied by 20 is 400
20 multiplied by 25 is 500
25 multiplied by 25 is 625
1 divided by 1 is 1
1 divided by 17 is 1
1 divided by 54 is 1
1 divided by 10 is 1
1 divided by 36 is 1
1 divided by 63 is 1
1 divided by 20 is 1
1 divided by 25 is 1
17 divided by 17 is 1
17 divided by 54 is 0
17 divided by 10 is 0
17 divided by 36 is 0
17 divided by 63 is 0
17 divided by 20 is 0
17 divided by 25 is 0
54 divided by 54 is 1
54 divided by 10 is 27
54 divided by 36 is 1.5
54 divided by 63 is 6
54 divided by 20 is 13.5
54 divided by 25 is 54
10 divided by 10 is 1
10 divided by 36 is 0.277778
10 divided by 63 is 1.11111
10 divided by 20 is 0.5
10 divided by 25 is 0.4
36 divided by 36 is 1
36 divided by 63 is 4
36 divided by 20 is 9
36 divided by 25 is 36
63 divided by 63 is 1
63 divided by 20 is 3.15
63 divided by 25 is 0.36
20 divided by 20 is 1
20 divided by 25 is 0.8
25 divided by 25 is 1

Answer 1

条件i <f1.size() && f2.size()应该写成i <f1.size() && i < f2.size()