# Make all array elements even by replacing any pair of array elements with their sum

Given an array **arr[]** consisting of **N** positive integers, the task is to make all array elements even by replacing any pair of array elements with their sum.

**Examples:**

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Input:arr[] = {5, 6, 3, 7, 20}Output:3Explanation:Operation 1:Replace arr[0] and arr[2] by their sum ( = 5 + 3 = 8) modifies arr[] to {8, 6, 8, 7, 20}.Operation 2:Replace arr[2] and arr[3] by their sum ( = 7 + 8 = 15) modifies arr[] to {8, 6, 15, 15, 20}.Operation 3:Replace arr[2] and arr[3] by their sum ( = 15 + 15 = 30) modifies arr[] to {8, 6, 30, 30, 20}.

Input:arr[] = {2, 4, 16, 8, 7, 9, 3, 1}Output:2

**Approach:** The idea is to keep replacing two odd array elements by their sum until all array elements are even. Follow the steps below to solve the problem:

- Initialize a variable, say
**moves**, to store the minimum number of replacements required. - Calculate the total number of odd elements present in the given array and store it in a variable, say
**cnt**. - If the value of
**cnt**is odd, then print**(cnt / 2 + 2)**as the result. Otherwise, print**cnt / 2**as the result.

Below is the implementation of the above approach:

## C++

`// C++ program for the above approach` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Function to find the minimum number` `// of replacements required to make` `// all array elements even` `void` `minMoves(` `int` `arr[], ` `int` `N)` `{` ` ` `// Stores the count of odd elements` ` ` `int` `odd_element_cnt = 0;` ` ` `// Traverse the array` ` ` `for` `(` `int` `i = 0; i < N; i++) {` ` ` `// Increase count of odd elements` ` ` `if` `(arr[i] % 2 != 0) {` ` ` `odd_element_cnt++;` ` ` `}` ` ` `}` ` ` `// Store number of replacements required` ` ` `int` `moves = (odd_element_cnt) / 2;` ` ` `// Two extra moves will be required` ` ` `// to make the last odd element even` ` ` `if` `(odd_element_cnt % 2 != 0)` ` ` `moves += 2;` ` ` `// Print the minimum replacements` ` ` `cout << moves;` `}` `// Driver Code` `int` `main()` `{` ` ` `int` `arr[] = { 5, 6, 3, 7, 20 };` ` ` `int` `N = ` `sizeof` `(arr) / ` `sizeof` `(arr[0]);` ` ` `// Function call` ` ` `minMoves(arr, N);` ` ` `return` `0;` `}` |

## Java

`// Java program for the above approach` `import` `java.util.*;` `class` `GFG{` `// Function to find the minimum number` `// of replacements required to make` `// all array elements even` `static` `void` `minMoves(` `int` `arr[], ` `int` `N)` `{` ` ` ` ` `// Stores the count of odd elements` ` ` `int` `odd_element_cnt = ` `0` `;` ` ` `// Traverse the array` ` ` `for` `(` `int` `i = ` `0` `; i < N; i++)` ` ` `{` ` ` `// Increase count of odd elements` ` ` `if` `(arr[i] % ` `2` `!= ` `0` `)` ` ` `{` ` ` `odd_element_cnt++;` ` ` `}` ` ` `}` ` ` `// Store number of replacements required` ` ` `int` `moves = (odd_element_cnt) / ` `2` `;` ` ` `// Two extra moves will be required` ` ` `// to make the last odd element even` ` ` `if` `(odd_element_cnt % ` `2` `!= ` `0` `)` ` ` `moves += ` `2` `;` ` ` `// Print the minimum replacements` ` ` `System.out.print(moves);` `}` `// Driver Code` `public` `static` `void` `main(String[] args)` `{` ` ` `int` `arr[] = { ` `5` `, ` `6` `, ` `3` `, ` `7` `, ` `20` `};` ` ` `int` `N = arr.length;` ` ` `// Function call` ` ` `minMoves(arr, N);` `}` `}` `// This code is contributed by shikhasingrajput` |

## C#

`// C# program for the above approach` `using` `System;` `public` `class` `GFG` `{` ` ` `// Function to find the minimum number` ` ` `// of replacements required to make` ` ` `// all array elements even` ` ` `static` `void` `minMoves(` `int` `[]arr, ` `int` `N)` ` ` `{` ` ` `// Stores the count of odd elements` ` ` `int` `odd_element_cnt = 0;` ` ` `// Traverse the array` ` ` `for` `(` `int` `i = 0; i < N; i++)` ` ` `{` ` ` `// Increase count of odd elements` ` ` `if` `(arr[i] % 2 != 0)` ` ` `{` ` ` `odd_element_cnt++;` ` ` `}` ` ` `}` ` ` `// Store number of replacements required` ` ` `int` `moves = (odd_element_cnt) / 2;` ` ` `// Two extra moves will be required` ` ` `// to make the last odd element even` ` ` `if` `(odd_element_cnt % 2 != 0)` ` ` `moves += 2;` ` ` `// Print the minimum replacements` ` ` `Console.Write(moves);` ` ` `}` ` ` `// Driver Code` ` ` `public` `static` `void` `Main(String[] args)` ` ` `{` ` ` `int` `[]arr = { 5, 6, 3, 7, 20 };` ` ` `int` `N = arr.Length;` ` ` `// Function call` ` ` `minMoves(arr, N);` ` ` `}` `}` `// This code is contributed by 29AjayKumar` |

## Python3

`# Python program for the above approach` `# Function to find the minimum number` `# of replacements required to make` `# all array elements even` `def` `minMoves(arr, N):` ` ` ` ` `# Stores the count of odd elements` ` ` `odd_element_cnt ` `=` `0` `;` ` ` `# Traverse the array` ` ` `for` `i ` `in` `range` `(N):` ` ` `# Increase count of odd elements` ` ` `if` `(arr[i] ` `%` `2` `!` `=` `0` `):` ` ` `odd_element_cnt ` `+` `=` `1` `;` ` ` `# Store number of replacements required` ` ` `moves ` `=` `(odd_element_cnt) ` `/` `/` `2` `;` ` ` `# Two extra moves will be required` ` ` `# to make the last odd element even` ` ` `if` `(odd_element_cnt ` `%` `2` `!` `=` `0` `):` ` ` `moves ` `+` `=` `2` `;` ` ` `# Prthe minimum replacements` ` ` `print` `(moves);` `# Driver Code` `if` `__name__ ` `=` `=` `'__main__'` `:` ` ` `arr ` `=` `[` `5` `, ` `6` `, ` `3` `, ` `7` `, ` `20` `];` ` ` `N ` `=` `len` `(arr);` ` ` `# Function call` ` ` `minMoves(arr, N);` ` ` `# This code is contributed by 29AjayKumar` |

## Javascript

`<script>` `// javascript program for the above approach` `// Function to find the minimum number` `// of replacements required to make` `// all array elements even` `function` `minMoves(arr, N)` `{` ` ` `// Stores the count of odd elements` ` ` `var` `odd_element_cnt = 0;` ` ` ` ` `var` `i;` ` ` `// Traverse the array` ` ` `for` `(i = 0; i < N; i++) {` ` ` `// Increase count of odd elements` ` ` `if` `(arr[i] % 2 != 0) {` ` ` `odd_element_cnt++;` ` ` `}` ` ` `}` ` ` `// Store number of replacements required` ` ` `var` `moves = Math.floor((odd_element_cnt)/2);` ` ` `// Two extra moves will be required` ` ` `// to make the last odd element even` ` ` `if` `(odd_element_cnt % 2 != 0)` ` ` `moves += 2;` ` ` `// Print the minimum replacements` ` ` `document.write(moves);` `}` `// Driver Code` ` ` `var` `arr = [5, 6, 3, 7, 20];` ` ` `N = arr.length;` ` ` `// Function call` ` ` `minMoves(arr, N);` `</script>` |

**Output:**

3

**Time complexity:** O(N)**Auxiliary Space:** O(1)