Recursion
What is it ?
Recursion in computer science is a method where the solution to a problem depends on solutions to smaller instances of the same problem (as opposed to iteration).
b4 = 4 * b3
= 4 * (3 * b2)
= 4 * (3 * (2 * b1))
= 4 * (3 * (2 * (1 * b0)))
= 4 * (3 * (2 * (1 * 1)))
= 4 * (3 * (2 * 1))
= 4 * (3 * 2)
= 4 * 6
= 24
Why recursion?
Where it's useful?
Let's see what notion do you have?
Function 1
void recursiveFunction(int num) { printf("%d\n", num); if (num < 4) recursiveFunction(num + 1); }
Function 2:
void recursiveFunction(int num) { if (num < 4) recursiveFunction(num + 1); printf("%d\n", num); }
Iterative approach involves four steps, initialization , condition, execution and updation.
In recursive function, only base condition (terminate condition) is specified.
#include<iostream>
using namespace std;
void combination(int i,int data[],int r,int n)
{
if(i==r) {
for(int k=1;k<=i;k++) cout<<data[k]<<" ";
cout<<"\n";
return ;
}
for(int j=1;j<=n;j++)
{
data[i+1]=j;
combination(i+1,data,r,n);
}
}
int main() {
int r,n;
r=3;
n=3;
int data[r+1];
combination(0,data,r,n);
return 0;
}Print all possible combinations of r elements in a given array
Copy of deck
By Khushboo Gupta
