# Implementation of Apriori Algorithm in C++

Here is C++ implementation of Apriori Algorithm.

```#include<iostream.h>
#include<conio.h>
void main()
{
int i,j,t1,k,l,m,f,f1,f2,f3;
//Initial item-purchase
int a[5][5];
for(i=0;i<5;i++)
{
cout<<"\n Enter items from purchase "<<i+1<<":";
for(j=0;j<5;j++)
{
cin>>a[i][j];
}
}
//Defining minimum level for acceptence
int min;
cout<<"\n Enter minimum acceptance level";
cin>>min;
//Printing initial input
cout<<"\nInitial Input:\n";
cout<<"\nTrasaction\tItems\n";
for(i=0;i<5;i++)
{
cout<<i+1<<":\t";
for(j=0;j<5;j++)
{
cout<<a[i][j]<<"\t";
}
cout<<"\n";
}
cout<<"\nAssume minimum support: "<<min;
//First pass
int l1[5];
for(i=0;i<5;i++)
{
t1=0;
for(j=0;j<5;j++)
{
for(k=0;k<5;k++)
{
if(a[j][k]==i+1)
{
t1++;
}
}
}
l1[i]=t1;
}
//Printing first pass
cout<<"\n\nGenerating C1 from data\n";
for(i=0;i<5;i++)
{
cout<<i+1<<": "<<l1[i]<<"\n";
}
//Second pass
//Counting number of possibilities for pass2
int p2pcount=0;
int p2items[5];
int p2pos=0;
for(i=0;i<5;i++)
{
if(l1[i]>=min)
{
p2pcount++;
p2items[p2pos]=i;
p2pos++;
}
}
//Printing selected items for second pass
cout<<"\nGenerating L1 From C1\n";
for(i=0;i<p2pos;i++)
{
cout<<p2items[i]+1<<"\t"<<l1[p2items[i]]<<"\n";
}
//Joining items
int l2[5][3];
int l2t1; //will hold first item for join
int l2t2; //will hold second item for join
int l2pos1=0; //position pointer in l2 array
int l2ocount=0; //product join occruance counter
int l2jcount=0; //join counter
for(i=0;i<p2pcount;i++)
{
for(j=i+1;j<p2pcount;j++)
{
l2t1=p2items[i]+1;
l2t2=p2items[j]+1;
if(l2t1==l2t2)
{
//it is self join
continue;
}
//join the elements
l2[l2pos1][0]=l2t1;
l2[l2pos1][1]=l2t2;
l2jcount++;
//count occurances
l2ocount=0; //reset counter
for(k=0;k<5;k++)
{
f1=f2=0; //resetting flag
//scan a purcahse
for(l=0;l<5;l++)
{
if(l2t1==a[k][l])
{
//one of the element found
f1=1;
}
if(l2t2==a[k][l])
{
//second elements also found
f2=1;
}
}
//one purchase scanned
if(f1==1&&f2==1) //both items are present in
purchase
{
l2ocount++;
}
}
//assign count
l2[l2pos1][2]=l2ocount;
l2pos1++;
}
}
//Printing second pass
cout<<"\n\nGenerating L2\n";
for(i=0;i<l2jcount;i++)
{
for(j=0;j<3;j++)
{
cout<<l2[i][j]<<"\t";
}
cout<<"\n";
}
//Third pass
int p3pcount=0;
int p3items[5]={-1,-1,-1,-1,-1};
int p3pos=0;
for(i=0;i<5;i++)
{
if(l2[i][2]>=min)
{
f=0;
for(j=0;j<5;j++)
{
if(p3items[j]==l2[i][0])
{
f=1;
}
}
if(f!=1)
{
p3items[p3pos]=l2[i][0];
p3pos++;
p3pcount++;
}
f=0;
for(j=0;j<5;j++)
{
if(p3items[j]==l2[i][1])
{
f=1;
}
}
if(f!=1)
{
p3items[p3pos]=l2[i][1];
p3pos++;
p3pcount++;
}
}
}
//Joining
int l3[5][4];
int l3ocount=0; //occurance counter
int l3jcount=0; //join counter
for(i=0;i<p3pcount;i++)
{
for(j=i+1;j<p3pcount;j++)
{
for(k=j+1;k<p3pcount;k++)
{
l3[i][0]=p3items[i];
l3[i][1]=p3items[j];
l3[i][2]=p3items[k];
l3jcount++;
//count occurances
l3ocount=0; //reset counter
for(k=0;k<5;k++)
{
f1=f2=f3=0; //resetting flag
//scan a purcahse
for(l=0;l<5;l++)
{
if(l3[i][0]==a[k][l])
{
//one of the element found
f1=1;
}
if(l3[i][1]==a[k][l])
{
//second elements also found
f2=1;
}
if(l3[i][2]==a[k][l])
{
//third element also found
f3=1;
}
}
//one purchase scanned
if(f1==1&&f2==1&&f3==1) //all items are present
in purchase
{
l3ocount++;
}
}
//assign count
l3[i][3]=l3ocount;
}
}
}
//Printing second pass
cout<<"\n\nGenerating L3\n";
for(i=0;i<l3jcount;i++)
{
for(j=0;j<4;j++)
{
cout<<l3[i][j]<<"\t";
}
cout<<"\n";
}
//Ending
getch();
}
/* Output
Enter items from purchase 1:1
5
2
0
0
Enter items from purchase 2:2
3
4
1
0
Enter items from purchase 3:3
4
0
0
0
Enter items from purchase 4:2
1
3
0
0
Enter items from purchase 5:1
2
3
0
0
Enter minimum acceptance level3
Initial Input:
Trasaction Items
1: 1 5 2 0 0
2: 2 3 4 1 0
3: 3 4 0 0 0
4: 2 1 3 0 0
5: 1 2 3 0 0
Assume minimum support: 3
Generating C1 from data
1: 4
2: 4
3: 4
4: 2
5: 1
Generating L1 From C1
1 4
2 4
3 4
Generating L2
1 2 4
1 3 3
2 3 3
Generating L3
1 2 3 3
*/
```

## 9 thoughts on “Implementation of Apriori Algorithm in C++”

1. chiranjivi sinha says:

hey i am getting this error when i compiling it in dev c++
1 21 C:\Users\chiranjiv\Desktop\Untitled2.cpp [Error] iostream.h: No such file or directory

Write #include(without .h )and “using namespace std;”

#include
using namespace std;

1. shubham says:

also showing error for the conio.h ……

1. chithra says:

yes….same error…what should i do ??

1. Replace

#include<iostream.h>
#include<conio.h>

with following three lines

#include<iostream>
#include<conio>
using namespace std;

3. MukeshChandra says:

keep only #include