added 3 way quick sort

other/3_way_quick_sort.cpp

@@ -0,0 +1,93 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+void print(long long arr[],long long n)
+{
+	for(int i=0;i<n;i++)
+		cout<<arr[i]<<" ";
+}
+
+pair<long long,long long> partition3(long long arr[],long long l,long long r )
+{
+	pair <long long,long long> par;
+	long long i=l,j,k=l,p=r;
+	while(i<p)
+	{
+		if(arr[i]<arr[r])
+			swap(arr[i++],arr[k++]);
+		else if(arr[i]==arr[r])
+			swap(arr[i],arr[--p]);
+		else
+			i++;
+	}
+	// print(arr,r+1);
+	// cout<<endl;
+	// cout<<k<<" "<<p<<endl;
+	long long temp=arr[r],end;
+	for(i=p-1,j=r;i>=k;i--,j--)
+		arr[j]=arr[i];
+	end=j;
+	for(j;j>=k;j--)
+		arr[j]=temp;
+	// print(arr,r+1);
+	// cout<<endl<<end;
+	par=make_pair(k,end);
+	return par;
+}
+
+void sort(long long arr[],long long l,long long r)
+{
+	if(l<r)
+	{
+		int k=l+rand()%(r-l+1);
+		swap(arr[l],arr[k]);
+		pair<long long,long long> par=partition3(arr,l,r);
+		sort(arr,l,par.first-1);
+		sort(arr,par.second+1,r);
+	}
+}
+bool checkSorted(long long arr[],long long n)
+{
+	int i;
+	for(i=0;i<n-1;i++)
+		if(arr[i]>arr[i+1])
+			return false;
+	return true;
+}
+
+int main()
+{
+	long long n,arr[100010];
+	cin>>n;
+	for(int i=0;i<n;i++)
+		cin>>arr[i];
+	sort(arr,0,n-1);
+	print(arr,n);
+	// partition3(arr,0,n-1);
+	return 0;
+}
+
+// int main()
+// {
+// 	long long n,ini[1000],temp,arr[1000],i;
+// 	n=100;
+// 	while(1)
+// 	{
+// 		srand(time(0));
+// 		for(i=0;i<n;i++)
+// 		{
+// 			temp=rand()%4;
+// 			arr[i]=temp;
+// 			ini[i]=temp;
+// 		}
+// 		sort(arr,0,n-1);
+// 		if(checkSorted(arr,n)==false)
+// 		{
+// 			print(ini,n);
+// 			cout<<endl;
+// 			print(arr,n);
+// 			return 0;
+// 		}
+// 	}
+// 	return 0;
+// }