Recursion for Coding Interviews in C++/

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Find the First Occurrence of a Number in an Array

Find the First Occurrence of a Number in an Array

This lesson will help you find the first occurrence of a number in an array using recursion.

We'll cover the following...

First Occurrence of a Number

Given an array, find the first occurrence of a given number in that array and return the index of that number.

The following illustration shows how to do it:

Implementing the Code

The following code explains how to find the first occurrence of a number in an array.

Experiment with the code by changing the values of array and x to see how it works!

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#include<iostream>
using namespace std;
// Recursive function
int firstOccurrence(int array[], int size, int x, int currentIndex){
    //base case
    if(size==currentIndex){//if array has been fully traversed and the element is not found
        return -1;     
    }
    if(array[currentIndex] == x){//if the value is found then return the index
        return currentIndex;
    }
    //recursive case
    return firstOccurrence(array,size,x,currentIndex+1); //call the recursive function
    
}
//Driver function
int main(){
    int array[] = {2,3,4,1,7,8,3};//define an array
    int x = 3;//define the number whose first occurence is to be found
    int size = 7;//define size of array
    cout<<"First Occurence of the number "<<x<<" is at index:";
    cout<<firstOccurrence(array,size,x,0);
    return 0;
}

Understanding the Code

A recursive code can be broken down into two parts. The ...