# Increment odd positioned elements by 1 and decrement even positioned elements by 1 in an Array

Given an array arr[], the task is increment all the odd positioned elements by 1 and decrement all the even positioned elements by 1.

Examples:

Input: arr[] = {3, 6, 8}
Output: 4 5 9

Input: arr[] = {9, 7, 3}
Output: 10 6 4

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: Traverse the array element by element and if the current element’s position is odd then increment it by 1 else decrement it by 1. Prin the contents of the updated array in the end.

Below is the implementation of the above approach:

 `// C++ implementation of the approach ` `#include ` `using` `namespace` `std; ` ` `  `// Utility function to print ` `// the contents of an array ` `void` `printArr(``int` `arr[], ``int` `n) ` `{ ` `    ``for` `(``int` `i = 0; i < n; i++) ` `        ``cout << arr[i] << ``" "``; ` `} ` ` `  `// Function to increment all the odd ` `// positioned elements by 1 and decrement ` `// all the even positioned elements by 1 ` `void` `updateArr(``int` `arr[], ``int` `n) ` `{ ` `    ``for` `(``int` `i = 0; i < n; i++) ` ` `  `        ``// If current element is odd positioned ` `        ``if` `((i + 1) % 2 == 1) ` `            ``arr[i]++; ` ` `  `        ``// If even positioned ` `        ``else` `            ``arr[i]--; ` ` `  `    ``// Print the updated array ` `    ``printArr(arr, n); ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `arr[] = { 3, 6, 8 }; ` `    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr[0]); ` `    ``updateArr(arr, n); ` ` `  `    ``return` `0; ` `} `

 `// Java implementation of the approach  ` `class` `GfG  ` `{  ` ` `  `// Utility function to print  ` `// the contents of an array  ` `static` `void` `printArr(``int` `arr[], ``int` `n)  ` `{  ` `    ``for` `(``int` `i = ``0``; i < n; i++)  ` `        ``System.out.print(arr[i] + ``" "``);  ` `}  ` ` `  `// Function to increment all the odd  ` `// positioned elements by 1 and decrement  ` `// all the even positioned elements by 1  ` `static` `void` `updateArr(``int` `arr[], ``int` `n)  ` `{  ` `    ``for` `(``int` `i = ``0``; i < n; i++)  ` ` `  `        ``// If current element is odd positioned  ` `        ``if` `((i + ``1``) % ``2` `== ``1``)  ` `            ``arr[i]++;  ` ` `  `        ``// If even positioned  ` `        ``else` `            ``arr[i]--;  ` ` `  `    ``// Print the updated array  ` `    ``printArr(arr, n);  ` `}  ` ` `  `// Driver code  ` `public` `static` `void` `main(String[] args)  ` `{  ` `    ``int` `arr[] = { ``3``, ``6``, ``8` `};  ` `    ``int` `n = arr.length;  ` `    ``updateArr(arr, n);  ` ` `  `}  ` `}  ` ` `  `// This code is contributed by Prerna Saini `

 `# Python3 implementation of the approach ` ` `  `# Utility function to print ` `# the contents of an array ` `def` `printArr(arr, n): ` `    ``for` `i ``in` `range``(``0``, n): ` `        ``print``(arr[i], end ``=` `" "``); ` ` `  `# Function to increment all the odd ` `# positioned elements by 1 and decrement ` `# all the even positioned elements by 1 ` `def` `updateArr(arr, n): ` `    ``for` `i ``in` `range``(``0``, n): ` ` `  `        ``# If current element is odd positioned ` `        ``if` `((i ``+` `1``) ``%` `2` `=``=` `1``): ` `            ``arr[i] ``+``=` `1``; ` ` `  `        ``# If even positioned ` `        ``else``: ` `            ``arr[i] ``-``=` `1``; ` ` `  `    ``# Print the updated array ` `    ``printArr(arr, n); ` ` `  `# Driver code ` `if` `__name__ ``=``=` `'__main__'``: ` `    ``arr ``=` `[``3``, ``6``, ``8``]; ` `    ``n ``=` `len``(arr); ` `    ``updateArr(arr, n); ` ` `  `# This code contributed by PrinciRaj1992 `

 `// C# implementation of the approach  ` `class` `GfG  ` `{  ` ` `  `// Utility function to print  ` `// the contents of an array  ` `static` `void` `printArr(``int` `[]arr, ``int` `n)  ` `{  ` `    ``for` `(``int` `i = 0; i < n; i++)  ` `        ``System.Console.Write(arr[i] + ``" "``);  ` `}  ` ` `  `// Function to increment all the odd  ` `// positioned elements by 1 and decrement  ` `// all the even positioned elements by 1  ` `static` `void` `updateArr(``int` `[]arr, ``int` `n)  ` `{  ` `    ``for` `(``int` `i = 0; i < n; i++)  ` ` `  `        ``// If current element is odd positioned  ` `        ``if` `((i + 1) % 2 == 1)  ` `            ``arr[i]++;  ` ` `  `        ``// If even positioned  ` `        ``else` `            ``arr[i]--;  ` ` `  `    ``// Print the updated array  ` `    ``printArr(arr, n);  ` `}  ` ` `  `// Driver code  ` `static` `void` `Main()  ` `{  ` `    ``int` `[]arr = { 3, 6, 8 };  ` `    ``int` `n = arr.Length;  ` `    ``updateArr(arr, n);  ` ` `  `}  ` `}  ` ` `  `// This code is contributed by mits `

 ` `

Output:
```4 5 9
```

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