How Can You Swap Two Variables Without Using a Third Variable?
Dec 09, 2024 pm 01:42 PMSwapping Variables Without a Third Variant
Introduction:
Swapping the values of two variables is a common programming task. Typically, a third variable is used as a temporary placeholder to facilitate the exchange. However, in some scenarios, it may be desirable to avoid creating an extra variable for memory optimization or other reasons.
Problem Statement:
Swap the values of two variables a and b without using a third variable.
Solution: XOR Swap Algorithm
The XOR swap algorithm leverages the XOR operator (^) to swap the contents of two variables. The algorithm is defined as:
void xorSwap(int* x, int* y) { if (x != y) { //ensure that memory locations are different *x ^= *y; *y ^= *x; *x ^= *y; } }
Implementation Details:
- The if statement checks if x and y have different memory locations to ensure they are not pointing to the same value.
- The XOR operator is applied three times to consecutively swap the values. Each XOR operation flips the bits of the corresponding variable, effectively exchanging their contents.
Example:
Let's demonstrate the algorithm with a = 10 and b = 15:
// Before swap a = 10 (00001010) b = 15 (00001111) // XOR step 1 a = a ^ b = 00001010 ^ 00001111 = 00000101 // XOR step 2 b = b ^ a = 00001111 ^ 00000101 = 00001010 // XOR step 3 a = a ^ b = 00000101 ^ 00001010 = 00001111 // After swap a = 15 b = 10
Considerations:
While the XOR swap algorithm can be efficient, it's generally not recommended for use in typical programming scenarios. Modern compilers can optimize the use of a temporary variable, making it more efficient to swap values in most cases.
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