R Examples

R - 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.

swap <- function(x, y) {
  cat("Before Swap:\n")
  cat("x =", x, "\n")
  cat("y =", y, "\n")

  #Swap technique
  x <- x + y
  y <- x - y
  x <- x - y

  cat("After Swap:\n")
  cat("x =", x, "\n")
  cat("y =", y, "\n") 
}

swap(10, 25)

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.

swap <- function(x, y) {
  cat("Before Swap:\n")
  cat("x =", x, "\n")
  cat("y =", y, "\n")

  #Swap technique
  x <- x * y
  y <- x / y
  x <- x / y

  cat("After Swap:\n")
  cat("x =", x, "\n")
  cat("y =", y, "\n") 
}

swap(10, 25)

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.

swap <- function(x, y) {
  cat("Before Swap:\n")
  cat("x =", x, "\n")
  cat("y =", y, "\n")

  #Swap technique
  x <- x / y
  y <- x * y
  x <- y / x

  cat("After Swap:\n")
  cat("x =", x, "\n")
  cat("y =", y, "\n") 
}

swap(10, 25)

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.