I am working on solving Euler project 3:
Description: The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?
This is my code to generate the answer. However I need an integer type to hold 600851475143
. When I compile this on GCC on a Mac I get:
integer constant is too large for ‘long’ type".
I expect long long could easily hold this number. I also tried making it unsigned. Why doesn't my code hold that small number and what can I do to make it work?
#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<numTo开发者_高级运维Test) // 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;
}
Check this question. You have to specify your literal like this:
600851475143LL
As @Space_C0wb0y said, you need to specify a suffix for the literal.
Also, you're going to have a problem with your IsPrimeFactor
function - the parameters are ints, but as you've already discovered, an int or even a long is not big enough to store the number you'll be passing in repeatedly...
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