Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Print all Semi-Prime Numbers less than or equal to N in C++
In this problem, we are given an integer N. and we have to print all the semiprime numbers that are less than or equal to N.
Before solving this problem, let’s understand what is a semi-prime number.
A semi-prime number is a number whose value is the product of two distinct prime numbers.
Let’s take an example,
21 = 3*7 is a semiprime number.
25 = 5*5 is not a semiprime number.
Now, let’s take an example of semiprime numbers less than or equal to n.
Input: N = 15 Output: 6 10 14 15
To solve this problem, we have to take each number less than equal to N and check if it has exactly two distinct prime factors.
Tip − we can also start our algorithm from 6 as the smallest semi-prime number is 6.
Example
#include <bits/stdc++.h>
using namespace std;
vector<int>generateSemiPrimeNumbers(int n){
int index[n + 1];
for (int i = 1; i <= n; i++)
index[i] = i;
int countDivision[n + 1];
for (int i = 0; i < n + 1; i++)
countDivision[i] = 2;
for (int i = 2; i <= n; i++) {
if (index[i] == i && countDivision[i] == 2) {
for (int j = 2 * i; j <= n; j += i) {
if (countDivision[j] > 0) {
index[j] = index[j] / i;
countDivision[j]--;
}
}
}
}
vector<int> semiPrime;
for (int i = 2; i <= n; i++) {
if (index[i] == 1 && countDivision[i] == 0) semiPrime.push_back(i);
}
return semiPrime;
}
int main(){
int n = 15;
cout<<"Semi-prime numbers less that or equal to "<<n<<"are :\n";
vector<int>semiPrime = generateSemiPrimeNumbers(n);
for (int i = 0; i < semiPrime.size(); i++)
cout<<semiPrime[i]<<"\t";
return 0;
}Output
Semi-prime numbers less than or equal to 15 are −
6 10 14 15
Updated on: 17-Jan-2020
253 Views
Advertisements