Given an unsorted array of distinct numbers, write a function that returns true if array consists of consecutive numbers.
Examples :
Input : arr[] = {5, 4, 2, 1, 3}
Output : Yes
Input : arr[] = {2, 1, 0, -3, -1, -2}
Output : Yes
We have discussed three different approaches in below post
Check if array elements are consecutive
In above post. three methods for this problem are discussed with the best time complexity of O(n) and in O(1) extra space but that solution doesn’t handle the case of negative numbers. So, in this post, a method with time complexity of O(n) and using O(1) space will be discussed which will handle the case of negative also. An important assumption here is elements are distinct.
- Find the sum of the array.
- If given array elements are consecutive that means they are in AP. So, find min element i.e. first term of AP then calculate ap_sum = n/2 * [2a +(n-1)*d] where d = 1. So, ap_sum = n/2 * [2a +(n-1)]
- Compare both sums. Print Yes if equal, else No.
C++
// C++ program for above implementation #include <bits/stdc++.h> using namespace std; // Function to check if elements are consecutive bool areConsecutives(int arr[], int n) { // Find minimum element in array int first_term = *(min_element(arr, arr + n)); // Calculate AP sum int ap_sum = (n * (2 * first_term + (n - 1) * 1)) / 2; // Calculate given array sum int arr_sum = 0; for (int i = 0; i < n; i++) arr_sum += arr[i]; // Compare both sums and return return ap_sum == arr_sum; } // Drivers code int main() { int arr[] = { 2, 1, 0, -3, -1, -2 }; int n = sizeof(arr) / sizeof(arr[0]); areConsecutives(arr, n) ? cout << "Yes" : cout << "No"; return 0; } |
Java
// Java program to check if array elements // are consecutive import java.io.*; class GFG { // Function to check if elements are // consecutive static Boolean areConsecutives(int arr[], int n) { // Find minimum element in array int first_term = Integer.MAX_VALUE; for (int j = 0; j < n; j++) { if(arr[j] < first_term) first_term = arr[j]; } // Calculate AP sum int ap_sum = (n * (2 * first_term + (n - 1) * 1)) / 2; // Calculate given array sum int arr_sum = 0; for (int i = 0; i < n; i++) arr_sum += arr[i]; // Compare both sums and return return ap_sum == arr_sum; } // Driver code public static void main(String[] args) { int arr[] = { 2, 1, 0, -3, -1, -2 }; int n = arr.length; Boolean result = areConsecutives(arr, n); if(result == true) System.out.println("Yes"); else System.out.println("No"); } } // This code is contributed by Prerna Saini |
Python 3
# Python 3 program for above # implementation import sys # Function to check if elements # are consecutive def areConsecutives(arr, n): # Find minimum element in array first_term = sys.maxsize for i in range(n): if arr[i] < first_term: first_term = arr[i] # Calculate AP sum ap_sum = ((n * (2 * first_term + (n - 1) * 1)) // 2) # Calculate given array sum arr_sum = 0 for i in range( n): arr_sum += arr[i] # Compare both sums and return return ap_sum == arr_sum # Driver Code arr = [ 2, 1, 0, -3, -1, -2 ] n = len(arr) if areConsecutives(arr, n): print( "Yes") else: print( "No") # This code is contributed # by ChitraNayal |
C#
// C# program to check if array // elements are consecutive using System; class GFG { // Function to check if elements // are consecutive static bool areConsecutives(int []arr, int n) { // Find minimum element in array int first_term = int.MaxValue; for (int j = 0; j < n; j++) { if(arr[j] < first_term) first_term = arr[j]; } // Calculate AP sum int ap_sum = (n * (2 * first_term + (n - 1) * 1)) / 2; // Calculate given array sum int arr_sum = 0; for (int i = 0; i < n; i++) arr_sum += arr[i]; // Compare both sums and return return ap_sum == arr_sum; } // Driver code public static void Main() { int []arr = {2, 1, 0, -3, -1, -2}; int n = arr.Length; bool result = areConsecutives(arr, n); if(result == true) Console.WriteLine("Yes"); else Console.WriteLine("No"); } } // This code is contributed by vt_m. |
PHP
<?php // PHP program to check if // array elements are consecutive // Function to check if elements // are consecutive function areConsecutives($arr, $n) { // Find minimum element in array $first_term = 9999999; for ($j = 0; $j < $n; $j++) { if($arr[$j] < $first_term) $first_term = $arr[$j]; } // Calculate AP sum $ap_sum = intval(($n * (2 * $first_term + ($n - 1) * 1)) / 2); // Calculate given array sum $arr_sum = 0; for ($i = 0; $i < $n; $i++) $arr_sum += $arr[$i]; // Compare both sums and return return $ap_sum == $arr_sum; } // Driver code $arr = array(2, 1, 0, -3, -1, -2); $n = count($arr); $result = areConsecutives($arr, $n); if($result == true) echo "Yes"; elseecho "No"; // This code is contributed by Sam007 ?> |
Javascript
<script> // Javascript program to check if array elements // are consecutive // Function to check if elements are // consecutive function areConsecutives(arr,n) { // Find minimum element in array let first_term = Number.MAX_VALUE; for (let j = 0; j < n; j++) { if(arr[j] < first_term) first_term = arr[j]; } // Calculate AP sum let ap_sum = (n * (2 * first_term + (n - 1) * 1)) / 2; // Calculate given array sum let arr_sum = 0; for (let i = 0; i < n; i++) arr_sum += arr[i]; // Compare both sums and return return ap_sum == arr_sum; } // Driver code let arr=[2, 1, 0, -3, -1, -2 ]; let n = arr.length; let result = areConsecutives(arr, n); if(result == true) document.write("Yes"); else document.write("No"); //This code is contributed by avanitrachhadiya2155 </script> |
Output :
Yes
Time Complexity : O(n)
Auxiliary Space : O(1)
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