Prime Factorization C++ Program

pratyushp21 · abranhe · commit 3931b00eb7de · 2020-10-10T22:11:00.000-04:00
Efficient Program to calculate all the Prime factors of a given number.
diff --git a/algorithms/math/Prime_Factorization.cpp b/algorithms/math/Prime_Factorization.cpp
@@ -0,0 +1,75 @@
+#include<iostream>
+#include<vector>
+using namespace std;
+vector<int>get_factors(vector<int>&primes,int n)
+{
+    vector<int>ans;
+    ans.clear();
+    for(int i=0;i*i<=n;i++)
+    {
+        if(n%primes[i]==0)
+        {
+            ans.push_back(primes[i]);
+            while(n%primes[i]==0)
+            {
+                n=n/primes[i];
+            }
+
+        }
+    }
+    if(n!=1)
+    {
+        ans.push_back(n);
+    }
+    return ans;
+} 
+vector<int>get_prime(vector<int>&prime,int n)
+{
+  for(int i=3;i<=1000;i+=2)
+  {
+    prime[i]=1;
+  }
+  //mark all the even number as non prime
+  for(int i=3;i*i<=1000;i+=2)
+  {
+    if(prime[i]==1)
+    {
+        for(int j=i*i;j<=1000;j+=i)
+        {
+            prime[j]=0;
+        }
+    }
+  }
+  prime[0]=prime[1]=0;
+  prime[2]=1;
+  vector<int>fectors;
+  for(int i=2;i<=1000;i++)
+  {
+   if(prime[i]==1)
+   {
+    fectors.push_back(i);
+   }
+  }
+return fectors;
+
+}
+int32_t main()
+{
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+    //first task to genrate prime fectors and store it
+      vector<int>p(1000,0);
+  //now we have all prime number till n
+    int n;
+    cin>>n;
+    //enter n (the number you want to get prime fector)
+    vector<int>primes=get_prime(p,n);
+    vector<int>ans=get_factors(primes,n);
+    cout<<"Prime Factors are :";
+    for(auto i:ans)
+    {
+        cout<<i<<" ";
+    }
+    cout<<endl;
+return 0;
+}
