To check that Given progression is Arithmetic or not ?

Question - 

Given an progression , you have to check that progression is Arithmetic or not ?

Example - 

Input : arr[] = {1,2,3,4,5}

Output : Arithmetic Progression

Input : arr[] = {2,4,6,8,9}

Output : Not Arithmetic progression

Approach - 

first we calculate d and check d with every element.

Implementation - 

//check that given progression is arithmetic or not

#include<iostream>

using namespace std;

void check(int arr[],int n)

{

int a=arr[0];

int d=arr[1]-arr[0];

int check=1;

for(int i=1;i<n-1;i++){

if((arr[i+1]-arr[i])!=d){

check=0;

break;

}

}

if(check==1)

cout<<"-->>Arithmetic progression"<<endl;

else

cout<<"Not Arithmetic progression"<<endl;

}

int main(int argc, char *argv[])

{

int n;

cout<<"Enter the number of element of Arithmetic progression : ";cin>>n;

int arr[n];

cout<<"Enter elements : "<<endl;

for(int i=0;i<n;i++)

cin>>arr[i];

check(arr,n);

return 0;

}

Code on compiler

Time complixity - O(n)