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fixed error by usage of prime numbers

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Christian Bender
2018-03-17 15:50:11 +01:00
committed by GitHub
parent d76510dfee
commit ead31b2c77
1 changed files with 71 additions and 50 deletions
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121
Math/Prime_Factorization/primefactorization.cpp
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@@ -1,4 +1,5 @@
#include <bits/stdc++.h>
#include <algorithm>
using namespace std;
// Declaring variables for maintaing prime numbers and to check whether a number is prime or not
@@ -9,63 +10,83 @@ vector<pair<int,int> > factors;
// Calculating prime number upto a given range
void SieveOfEratosthenes(int N)
{
memset(isprime, true, sizeof isprime);
for(int i=2; i<=N ;i++)
{
if(isprime[i])
{
for(int j=2*i; j<=N; j+=i)
isprime[j]=false;
}
}
for(int i=2;i<=N;i++)
{
if(isprime[i])
prime_numbers.push_back(i);
}
return;
// initializes the array isprime
memset(isprime, true, sizeof isprime);
for(int i=2; i<=N ; i++)
{
if(isprime[i])
{
for(int j=2*i; j<=N; j+=i)
isprime[j]=false;
}
}
for(int i=2; i<=N; i++)
{
if(isprime[i])
prime_numbers.push_back(i);
}
}
void printDebug()
{
// Prime factors with their powers in the given number in new line
for(auto it: prime_numbers)
{
cout<< it << endl;
}
}
// Prime factorization of a number
void prime_factorization(int num)
{
for(int i=0; prime_numbers[i]<=num; i++)
{
int count=0;
while(num%prime_numbers[i] == 0)
{
count++;
num = num/prime_numbers[i];
}
if(count)
factors.push_back(make_pair(prime_numbers[i],count));
}
if(num>2)
factors.push_back(make_pair(num,1));
return;
vector<int>::iterator it;
it = find (prime_numbers.begin(), prime_numbers.end(), num);
if (it == prime_numbers.end())
{
for(int i=0; prime_numbers[i]<=num; i++)
{
int count=0;
while(num%prime_numbers[i] == 0)
{
count++;
num = num/prime_numbers[i];
}
if(count)
factors.push_back(make_pair(prime_numbers[i],count));
}
}
else
{
factors.push_back(make_pair(num,1));
}
// if(num>2)
// factors.push_back(make_pair(num,1));
}
int main()
{
int num;
cin>>num;
SieveOfEratosthenes(num);
prime_factorization(num);
// Prime factors with their powers in the given number in new line
for(auto it: factors)
{
cout<<it.first<<" "<<it.second<<endl;
}
return 0;
int num;
cout << "\t\tComputes the prime factorization\n\n";
cout << "Type in a number: ";
cin>>num;
SieveOfEratosthenes(num);
prime_factorization(num);
// Prime factors with their powers in the given number in new line
for(auto it: factors)
{
cout<<it.first<<" "<<it.second<<endl;
}
return 0;
}