Created PrimeNumbers.c

	// Question : Calculate number of prime factors of all numbers from 1 to nos

Author: destinyson7

Math/PrimeNumbers.c

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+#include<stdio.h>
+int lp[1000000];
+int main()
+{
+	// Question : Calculate number of prime factors of all numbers from 1 to nos 
+	// nos >=1 && nos<=100000
+	// For example if nos = 5 , Ans = (1-> 0) + (2->1) + (3->1) + (4->2) + (5->1) = 5
+	// Time Complexity = (O(nlogn))
+	int nos;
+	scanf("%d",&nos);
+	for(int i=2;i<=nos;i++)
+	{
+		// lp array stores the lowest prime factor that divides nos
+		// for example lp[4]=2 lp[49]=7
+		if(lp[i]==0)
+		{
+			lp[i]=i;
+			for(int j=2*i;j<=nos;j+=i)
+			{
+				if(lp[j]==0)
+					lp[j]=i;
+			}
+		}
+	}
+	int ans=0;
+	for(int i=1;i<=nos;i++)
+	{
+		int temp=i;
+		while(lp[temp]!=0)
+		{
+			temp/=lp[temp];
+			ans++;
+		}
+	}
+	printf("%d\n",ans);
+}