Given an array of N positive integers. The task is to check if the array is sorted in wave form.
Examples:
Input: arr[] = {1, 2, 3, 4, 5}
Output: NO
Input: arr[] = {1, 5, 3, 7, 2, 8, 6}
Output: YES
Approach:
- First check the element at index 1, i.e, A[1] and observe the pattern.
- If arr[1] is greater than its left and right element, then this pattern will be followed by other elements.
- Else If arr[1] is smaller than its left and right element, then this pattern will be followed by other elements.
- Check for the same pattern found from above steps. If at any point, this rule violates, return false, else return true.
Below is the implementation of above approach:
C++
// CPP code to check if the array is wave array #include <iostream> using namespace std; // Function to check if array is wave array // arr : input array // n : size of array bool isWaveArray(int arr[], int n) { bool result = true; /* Check the wave form * If arr[1] is greater than left and right * Same pattern will be followed by whole * elements, else reverse pattern * will be followed by array elements */ if (arr[1] > arr[0] && arr[1] > arr[2]) { for (int i = 1; i < n - 1; i += 2) { if (arr[i] > arr[i - 1] && arr[i] > arr[i + 1]) { result = true; } else { result = false; break; } } // Check for last element if (result == true && n % 2 == 0) { if (arr[n - 1] <= arr[n - 2]) { result = false; } } } else if (arr[1] < arr[0] && arr[1] < arr[2]) { for (int i = 1; i < n - 1; i += 2) { if (arr[i] < arr[i - 1] && arr[i] < arr[i + 1]) { result = true; } else { result = false; break; } } // Check for last element if (result == true && n % 2 == 0) { if (arr[n - 1] >= arr[n - 2]) { result = false; } } } return result; } // Driver Code int main() { // Array int arr[] = { 1, 3, 2, 4 }; int n = sizeof(arr) / sizeof(int); if (isWaveArray(arr, n)) { cout << "YES" << endl; } else { cout << "NO" << endl; } return 0; } |
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Java
// Java code to check if the array is wave array public class GFG { // Function to check if array is wave array // arr : input array // n : size of array static boolean isWaveArray(int arr[], int n) { boolean result = true; /* Check the wave form * If arr[1] is greater than left and right * Same pattern will be followed by whole * elements, else reverse pattern * will be followed by array elements */ if (arr[1] > arr[0] && arr[1] > arr[2]) { for (int i = 1; i < n - 1; i += 2) { if (arr[i] > arr[i - 1] && arr[i] > arr[i + 1]) { result = true; } else { result = false; break; } } // Check for last element if (result == true && n % 2 == 0) { if (arr[n - 1] <= arr[n - 2]) { result = false; } } } else if (arr[1] < arr[0] && arr[1] < arr[2]) { for (int i = 1; i < n - 1; i += 2) { if (arr[i] < arr[i - 1] && arr[i] < arr[i + 1]) { result = true; } else { result = false; break; } } // Check for last element if (result == true && n % 2 == 0) { if (arr[n - 1] >= arr[n - 2]) { result = false; } } } return result; } // Driver code public static void main(String args[]) { int arr[] = { 1, 3, 2, 4 }; int n = arr.length; if (isWaveArray(arr, n)) { System.out.println("YES"); } else { System.out.println("NO"); } } // This Code is contributed by ANKITRAI1 } |
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Python 3
# Python 3 code to check if # the array is wave array # Function to check if # array is wave array # arr : input array # n : size of array def isWaveArray(arr , n): result = True # Check the wave form # If arr[1] is greater than # left and right. Same pattern # will be followed by whole # elements, else reverse pattern # will be followed by array elements if (arr[1] > arr[0] and arr[1] > arr[2]): for i in range(1, n - 1, 2): if (arr[i] > arr[i - 1] and arr[i] > arr[i + 1]): result = True else : result = False break # Check for last element if (result == True and n % 2 == 0): if (arr[n - 1] <= arr[n - 2]) : result = False elif (arr[1] < arr[0] and arr[1] < arr[2]) : for i in range(1, n - 1, 2) : if (arr[i] < arr[i - 1] and arr[i] < arr[i + 1]): result = True else : result = False break # Check for last element if (result == True and n % 2 == 0) : if (arr[n - 1] >= arr[n - 2]) : result = False return result # Driver Code if __name__ == "__main__": # Array arr = [ 1, 3, 2, 4 ] n = len(arr) if (isWaveArray(arr, n)): print("YES") else: print("NO") # This code is contributed # by ChitraNayal |
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C#
// C# code to check if the // array is wave array using System; class GFG { // Function to check if array // is wave array // arr : input array // n : size of array static bool isWaveArray(int []arr, int n) { bool result = true; /* Check the wave form * If arr[1] is greater than left * and right. Same pattern will be * followed by whole elements, else * reverse pattern will be followed by array elements */ if (arr[1] > arr[0] && arr[1] > arr[2]) { for (int i = 1; i < n - 1; i += 2) { if (arr[i] > arr[i - 1] && arr[i] > arr[i + 1]) { result = true; } else { result = false; break; } } // Check for last element if (result == true && n % 2 == 0) { if (arr[n - 1] <= arr[n - 2]) { result = false; } } } else if (arr[1] < arr[0] && arr[1] < arr[2]) { for (int i = 1; i < n - 1; i += 2) { if (arr[i] < arr[i - 1] && arr[i] < arr[i + 1]) { result = true; } else { result = false; break; } } // Check for last element if (result == true && n % 2 == 0) { if (arr[n - 1] >= arr[n - 2]) { result = false; } } } return result; } // Driver code public static void Main() { int []arr = { 1, 3, 2, 4 }; int n = arr.Length; if (isWaveArray(arr, n)) { Console.WriteLine("YES"); } else { Console.WriteLine("NO"); } } } // This code is contributed // by inder_verma |
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PHP
<?php // PHP code to check if the array is wave array // Function to check if array is wave array // arr : input array // n : size of array function isWaveArray( $arr, $n) { $result = true; /* Check the wave form * If arr[1] is greater than left and right * Same pattern will be followed by whole * elements, else reverse pattern * will be followed by array elements */ if ($arr[1] > $arr[0] && $arr[1] > $arr[2]) { for ( $i = 1; $i < ($n - 1); $i += 2) { if ($arr[$i] > $arr[$i - 1] && $arr[$i] > $arr[$i + 1]) { $result = true; } else { $result = false; break; } } // Check for last element if ($result == true && $n % 2 == 0) { if ($arr[$n - 1] <= $arr[$n - 2]) { $result = false; } } } else if ($arr[1] < $arr[0] && $arr[1] < $arr[2]) { for ($i = 1; $i < $n - 1; $i += 2) { if ($arr[$i] < $arr[$i - 1] && $arr[$i] < $arr[$i + 1]) { $result = true; } else { $result = false; break; } } // Check for last element if ($result == true && $n % 2 == 0) { if ($arr[$n - 1] >= $arr[$n - 2]) { $result = false; } } } return $result; } // Driver Code // Array $arr = array (1, 3, 2, 4 ); $n = sizeof($arr); if (isWaveArray($arr, $n)) { echo "YES"; } else { echo "NO"; } // This code is contributed by jit_t ?> |
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Output:
YES
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