Swap two elements of 1D array in C++

In this tutorial, we will learn how to swap two elements in a one-dimensional array. This we will see through either using a manual swap function or a built-in swap function in C++. Hope you will like this tutorial. Let’s get started.

Swap two elements of a 1D array in C++

To swap two elements in a 1D array we can do it in two ways. First, we will do it manually, and second, we will do using the built-in C++ function that swap() method.

Suppose we are given a 1D array such as an array having size 6 and we want to swap two elements having values 1 and 3 so that the array becomes sorted in decreasing order.

array[6] = {5,4,1,2,3,0}

After swap we will have array[6] = {5,4,3,2,1,0}.

Steps to Swap two elements.

1. First, create a temporary variable such as temp and store the value of that particular index.
2. Then, the value of the second index in the first index.
3. Lastly, store the temp value in the second index.

Let’s understand with example code. Then it will be very clear.

#include <iostream>

using namespace std;

void printArr (int arr[], int length) {
    for(int i = 0; i < length; i++) {
        cout << arr[i] << " ";
    }
    cout << endl;
}

int main() {

  // declare array
  const int length = 5;
  int arr[length] = {5, 2, 3, 4, 1};

  // temp variable in swapping
  int temp;

  cout << "Original array: ";
  printArr(arr, length);

  // swapping second and fourth element
  temp = arr[1];
  arr[1] = arr[3];
  arr[3] = temp;

  cout << "Array with second and fourth element swapped and sorted: ";
  printArr(arr, length);

  return 0;
}

OUTPUT:
Original array: 5 2 3 4 1 
Array with second and fourth element swapped and sorted: 5 4 3 2 1

Now we will see using the built-in swap() function in C++. This function helps in swapping two elements without using a third variable such as the temp variable as we used in the above case.

Syntax :

void swap(int var1, int var2)

#include <iostream>
using namespace std;

void printArr (int arr[], int size) {
    for(int i = 0; i < size; i++) {
        cout << arr[i] << " ";
    }
    cout << endl;
}

int main() {
    
  const int size = 5;
  int arr[size] = {5, 2, 3, 4, 1};
  
  cout << "Original array: ";
  printArr(arr, size);

  swap(arr[1], arr[3]); // built-in swap() method

  cout << "Array with second and fourth element swapped: ";
  printArr(arr, size);

  return 0;
}

OUTPUT:

Original array: 5 2 3 4 1
Array with second and fourth element swapped: 5 4 3 2 1

Hope you liked this tutorial. Keep Learning !!!!

Also Read: C++ Null Pointers with examples