From ead31b2c7724091e2b139a221e3424dba58b05f9 Mon Sep 17 00:00:00 2001
From: Christian Bender <christianbender89@web.de>
Date: Sat, 17 Mar 2018 15:50:11 +0100
Subject: [PATCH] fixed error by usage of prime numbers

---
 .../primefactorization.cpp                    | 121 ++++++++++--------
 1 file changed, 71 insertions(+), 50 deletions(-)

diff --git a/Math/Prime_Factorization/primefactorization.cpp b/Math/Prime_Factorization/primefactorization.cpp
index 8a17badd7..fdf836f24 100644
--- a/Math/Prime_Factorization/primefactorization.cpp
+++ b/Math/Prime_Factorization/primefactorization.cpp
@@ -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;
 }