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这个程序不会用大数字运行

variables c++

samuraiseoul · 技术社区 · 14 年前

#include <iostream>

using namespace std;

bool prime (long long recievedvalue) { //starts a function that returns a boolean with parameters being a factor from a number
    long long j =1;
    long long remainderprime = 0;
    bool ended = false;
    while (ended == false){ //runs loop while primality is undetermined
        if (recievedvalue == 1){ //if the recieved value is a 1 it isn't prime
            //not prime
            return false;
            break; // breaks loop
            }
        remainderprime=recievedvalue%j; //gives a remainder for testing
        if ((remainderprime==0 && j>2) && (j!=recievedvalue || j == 4)){ //shows under which conditions it isn't prime
        ended=true;
        //not prime
        return false;
        }
        else if (j==1){
            j++;
            }
        else if ( recievedvalue==2 || j==recievedvalue ){ // shows what conditions it is prime
          ended = true;
          //prime
          return true;
            }
            else {
            j++;
            }
        }
    }


long long multiple(long long tbfactor){ //factors and then checks to see if factors are prime, then adds all prime factors together
    //parameter is number to be factored
    long long sum = 0;
    bool primetest = false;
    long long remainderfact;
    long long i=1;
    while (i<=tbfactor){ //checks if a i is a factor of tbfactor
        remainderfact=tbfactor%i;
        if (remainderfact==0){ //if it is a factor it checks if it is a prime
            primetest = prime(i);
        }
        if (primetest ==true){ //if it is prime it add that to the sum
            sum += i;
            primetest=false;
        }
        i++;
    }
    return sum;
}

int main()
{
    long long input;
    long long output;
    cout << "Enter a number > 0 to find the sum of all it's prime factors: ";
    cin >> input;
    if (input == 0 || input <= 0){
        cout << "The number you entered was too small."<< endl << "Enter number a number to find the sum of all it's prime factors: ";
    cin >> input;
        }
    output = multiple(input);
    cout << output << endl << "finished";
    return 0;
}

现在可以肯定的是,无论它是否是int,问题都会做同样的事情。就像我说的,我是编程新手,所以我很期待你的回复。:)

2 回复 | 直到 14 年前

San Jacinto 14 年前

我很乐意你的程序正在运行。我肯定会有人突然出现,马上给你答案,但我希望这不会发生,这样你就可以体验到我几年前遇到这个问题时做的同样的事情。

这样做:从1开始,然后用2的幂(1,2,4,8,16等)继续,每次输入两倍。它什么时候“停止运行?”是不是越来越慢了?

josh 14 年前

如果你想知道一个数是否是素数,这里有一个快速的解决方案,

#include <iostream>

using namespace std;

#define ullong unsigned long long

bool prime (ullong x)
{
    if(x <= 1)
        return false;

    ullong s = (ullong)sqrt(x);

    for(ullong i=2;i<=s;i++)
        if(x%i == 0)
            return false;

    return true;
}