Question

我正致力于解决欧拉项目3：

Description: The prime factors of 13195 are 5, 7, 13 and 29.
             What is the largest prime factor of the number 600851475143 ?

这是我生成答案的代码。但是我需要一个整数类型来保存600851475143。当我在Mac上的GCC上编译它时，我得到：

integer constant is too large for ‘long’ type".

我希望很长一段时间可以很容易地保持这个数字。我也试过让它没有签名。为什么我的代码不能保留那么少的代码，我该怎么做才能使它工作？

#include <iostream>
#include <vector>

using namespace std;

static bool IsPrimeFactor(int numToTest,int testNum,vector<int> factors)
{
    if(numToTest%testNum==0) // is it a factor?
    {
        // see if it is a prime factor
        for(unsigned int i=0; i < factors.size(); i++)
        {
            if(testNum%factors[i]==0)  // see if this factor
            {                          //is divisble by one we have already

                return false;
            }
        }

        return true;
    }
    return false;
}

int main() {
    unsigned long long numToTest=600851475143;
    unsigned int testNum=2;  // 0 and 1 are assumed
    vector<int> factors;   

    while(testNum<numToTest)   // don't go higher than the max num
    {
        if(IsPrimeFactor(numToTest,testNum,factors)) // is it a factor?
        {
            factors.push_back(testNum); // got through prime factors 
        }                                   // and none divided it

        testNum++;
    }

    for(unsigned int i=0; i < factors.size(); i++)
    {
        cout << "factor " <<factors[i] << endl;
    }

    cout<<"Highest factor: " << factors[factors.size()-1]<<endl;

    return 0;
}

Answer 1

检查this问题。你必须像这样指定你的文字：

600851475143LL

Answer 2

正如@Space_C0wb0y所说，你需要为文字指定一个后缀。

另外，你的IsPrimeFactor函数会出现问题 - 参数是整数，但正如你已经发现的那样，一个int甚至一个long都不足以存储你的数字我会反复传递......

当找到最大素数因子时，“整数常数对于'long'类型来说太大了”

2 个答案: