Question

How to check if a sequence of numbers is an Arithmetic progression (consecutive differences are the same) in C++

Answer 1

#include <iostream>
#include <algorithm>

bool isArithmeticProgression(int arr[], int size) {
    if (size == 1) {
        return true;
    }

    std::sort(arr, arr + size);

    int difference = arr[1] - arr[0];
    for (int i = 2; i < size; i++) {
        if (arr[i] - arr[i - 1] != difference) {
            return false;
        }
    }

    return true;
}

int main()
{
    int arr[] = {10, 20, 15, 5, 25, 35, 30};
    int size = sizeof(arr) / sizeof(arr[0]);

    (isArithmeticProgression(arr, size)) ? (std::cout << "Yes") : (std::cout << "No");
}



/*
run:

yes

*/

 

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Answer 2

#include <climits>
#include <iostream>
#include <unordered_set>

bool isArithmeticProgression(int arr[], int size) {
    if (size == 1) {
        return true;
    }
 
    std::unordered_set<int> uset;
    int max = INT_MIN;
    int min = INT_MAX;
    for (int i = 0; i < size; i++) {
        max = std::max(arr[i], max);
        min = std::min(arr[i], min);
        uset.insert(arr[i]);
    }
    
    int difference = (max - min) / (size - 1);
    int count = 0;
 
    while (uset.find(max) != uset.end()) {
        count++;
        max = max - difference;
    }
    
    if (count == size) {
        return true;
    }
 
    return false;
}
 
int main()
{
    int arr[] = {10, 20, 15, 5, 25, 35, 30};
    int size = sizeof(arr) / sizeof(arr[0]);
 
    (isArithmeticProgression(arr, size)) ? (std::cout << "Yes") : (std::cout << "No");
}
 
 
 
/*
run:
 
yes
 
*/

 

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