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prime_factorization.cpp
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81 lines (66 loc) · 1.58 KB
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#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
// Declaring variables for maintaing prime numbers and to check whether a number is prime or not
bool isprime[1000006];
vector<int> prime_numbers;
vector<pair<int, int>> factors;
// Calculating prime number upto a given range
void SieveOfEratosthenes(int N)
{
// 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);
}
}
// Prime factorization of a number
void prime_factorization(int num)
{
int number = num;
for (int i = 0; prime_numbers[i] <= num; i++)
{
int count = 0;
// termination condition
if (number == 1)
{
break;
}
while (number % prime_numbers[i] == 0)
{
count++;
number = number / prime_numbers[i];
}
if (count)
factors.push_back(make_pair(prime_numbers[i], count));
}
}
/*
I added a simple UI.
*/
int main()
{
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;
}