Fastest way to find prime number

Author: Pankajcoder1

best_approach/Sieve_of_Eratosthenes_prime_number.cpp

@@ -0,0 +1,101 @@
+/*
+    written by Pankaj Kumar.
+    country:-INDIA
+*/
+#include <bits/stdc++.h>
+#include <ext/pb_ds/assoc_container.hpp>
+#include <ext/pb_ds/tree_policy.hpp>
+using namespace std;
+using namespace __gnu_pbds;
+typedef long long ll ;
+typedef vector<ll> vl;
+#define speed cin.tie(0);cout.tie(0);ios_base::sync_with_stdio(0);
+// define values.
+// #define mod 1000000007
+#define phi 1.618
+/*  Abbrevations  */
+#define ff first
+#define ss second
+#define mp make_pair
+#define line cout<<endl;
+#define pb push_back
+#define Endl "\n"
+// loops
+#define forin(arr,n) for(ll i=0;i<n;i++) cin>>arr[i];
+// Some print
+#define no cout<<"NO"<<endl;
+#define yes cout<<"YES"<<endl;
+#define cc ll test;cin>>test;while(test--)
+// sort
+#define all(V) (V).begin(),(V).end()
+#define srt(V) sort(all(V))
+#define srtGreat(V) sort(all(V),greater<ll>())
+#define printv(v) for(ll i=0;i<ll(v.size());i++){cout<<v[i]<<" ";} line;
+// some extra
+#define sz(V) ll(V.size())
+/* ONLINE JUDGE */
+// #ifdef ONLINE_JUDGE
+//     freopen("input.txt", "r", stdin);freopen("output.txt", "w", stdout);
+// #endif
+// function
+
+ll power(ll x,ll y,ll mod)
+{
+    ll res=1;
+    // x=x%mod;
+    while(y>0)
+    {
+        if(y%2==1)
+        {
+            res*=x;
+            // res=res%mod;
+        }
+        y/=2; x*=x; // x=x%mod;
+    }
+    return res;
+}
+// datatype definination
+#define ordered_set tree<ll,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update>
+
+/* ascii value 
+A=65,Z=90,a=97,z=122
+*/
+/*  -----------------------------------------------------------------------------------*/
+
+ll solve()
+{
+    cout<<"This is to print all prime number smaller of equal to given number."<<endl;
+    ll n;
+    cin>>n;
+    vector<bool> prime(n+1,true);
+    for(ll i=2;i*i<=n;i++)
+    {
+        if(prime[i])
+        {
+            for(ll j=i*i;j<n;j+=i)
+                prime[j]=false;
+        }
+    }
+    cout<<"List of all prime number is: ";
+    for(ll i=2;i<=n;i++)
+    {
+        if(prime[i])
+            cout<<i<<" ";
+    }
+    line;
+    return 0;
+}
+
+int main()
+{
+    speed;
+    // freopen("input.txt","r",stdin);
+    // freopen("output.txt","w",stdout);
+    solve();
+}
+
+/* stuff you should look before submission 
+* int overflow
+* special test case (n=0||n=1||n=2)
+* don't get stuck on one approach if you get wrong answer
+*/