C++ - Swap two numbers


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There are two common ways to swap the value of two variables:

  • Swap the value of two variables using a temporary variable
  • Swap the value of two variables without using temporary variable

Example: Swap the value of two variables using a temporary variable

In the below example, the initial value of variables x and y are 10 and 25. A temporary variable called temp is created to store the value of x and then the value of y is assigned to x. Finally, value of temp (which stores values of x) is assigned to variable y. The final value of variables x and y after swap are 25 and 10 respectively.

#include <iostream>
using namespace std;

static void swap(int, int);

static void swap(int x, int y) {
    cout<<"Before Swap.\n";
    cout<<"x = "<<x<<"\n";
    cout<<"y = "<<y<<"\n";

    //Swap technique
    int temp = x;
    x = y;
    y = temp;

    cout<<"After Swap.\n";
    cout<<"x = "<<x<<"\n";
    cout<<"y = "<<y<<"\n";
}

int main() {
  swap(10, 25);
  return 0;
}

Output

Before Swap.
x = 10
y = 25
After Swap.
x = 25
y = 10

Example: Swap the value of two variables without using temporary variable

+ operator is used to swap the value of two variables. In this method no temporary variable is used. Please see the example below for syntax.

#include <iostream>
using namespace std;

static void swap(int, int);

static void swap(int x, int y) {
    cout<<"Before Swap.\n";
    cout<<"x = "<<x<<"\n";
    cout<<"y = "<<y<<"\n";

    //Swap technique
    x = x + y;
    y = x - y;
    x = x - y;

    cout<<"After Swap.\n";
    cout<<"x = "<<x<<"\n";
    cout<<"y = "<<y<<"\n";
}

int main() {
  swap(10, 25);
  return 0;
}

Output

Before Swap.
x = 10
y = 25
After Swap.
x = 25
y = 10

Similarly, others operators can also be used in this method. Please see the page: C++ - Swap two numbers without using Temporary Variable.



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