C++ Examples

C++ - Swap two numbers without using Temporary Variable

The value of two variables can be swapped without using any temporary variables. The method involves using operators like +, *, / and bitwise.

Method 1: Using + operator

In the below example, the + operator is used to swap the value of two variables x and y.

#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;
}

The above code will give the following output:

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

Method 2: Using * operator

Like + operator, the * operator can also be used to swap the value of two variables x and y.

#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;
}

The above code will give the following output:

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

Method 3: Using / operator

Similarly / operator can also be used to swap the value of two variables x and y.

#include <iostream>
using namespace std;

static void swap(float, float);

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

  //Swap technique
  x = x / y;
  y = x * y;
  x = y / x;

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

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

The above code will give the following output:

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

Method 4: Using bitwise operator

The bitwise XOR (^) operator can also be used to swap the value of two variables x and y. It returns 1 when one of two bits at same position in both operands is 1, otherwise returns 0.

#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;
}

The above code will give the following output:

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

Disadvantages of using above methods

The multiplication and division based approaches fail if the value of one of the variable is 0.
The addition based approach may fail due to arithmetic overflow. If x and y are too large, operation performed on operands may result into out of range integer.

C++ - Swap two numbers without using Temporary Variable

Method 1: Using + operator

Method 2: Using * operator

Method 3: Using / operator

Method 4: Using bitwise operator

Disadvantages of using above methods

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