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 example below, 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.
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