cpp-basic-codes/Sieve-of-Eratosethenes.cpp at main · Ankit-Rattan/cpp-basic-codes · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
// Prime numbers using Sieve of Eratosthenes

#include <iostream>

using namespace std;

void primeSieve(int n){
    int count=0;
    int prime[100]={0};
    for(int i=2; i<=n; i++){
        if(prime[i]==0){
            for(int j=i*i; j<=n; j+=i){
                prime[j]=1;
            }
        }
    }
    for(int i=2; i<=n; i++){
        if(prime[i]==0){
            count++;
            cout<<i<<" ";

        }
    }
    cout<<endl;
    cout<<"Total numbers of prime number is :";
    cout<<count<<endl;
}

int main()
{
    int n;
    cin>>n;
    primeSieve(n);


    return 0;
}


// Prime factorisation using Sieve

#include <iostream>

using namespace std;

void primeFactor(int n){
    int spf[100]={0};
    for(int i=2; i<=n; i++){
        spf[i]=i;
    }
    for(int i=2; i<=n; i++){
        if(spf[i]==i){
            for(int j=i*i; j<=n; j+=i){
                if(spf[j]==j){
                    spf[j]=i;
                }
            }
        }
    }
    while(n!=1){
        cout<<spf[n]<<" ";
        n=n/spf[n];
    }

}

int main()
{
    int n;
    cin>>n;
    primeFactor(n);


    return 0;
}