Cracking the Coding Interview, 4 Edition - 150 Programming Interview Questions and Solutions

Solutions to Chapter 19 | Moderate
19.1 Write a function to swap a number in place without temporary variables.
pg 89
SOLUTION
This is a classic interview problem. If you haven’t heard this problem before, you can approach
it by taking the difference between a and b:
1 public static void swap(int a, int b) {
2 a = b - a; // 9 - 5 = 4
3 b = b - a; // 9 - 4 = 5
4 a = a + b; // 4 + 5 = 9
5
6 System.out.println(“a: “ + a);
7 System.out.println(“b: “ + b);
8 }
You can then optimize it as follows:
1 public static void swap_opt(int a, int b) {
2 a = a^b;
3 b = a^b;
4 a = a^b;
5
6 System.out.println(“a: “ + a);
7 System.out.println(“b: “ + b);
8 }
2 6 5
Cracking the Coding Interview | Additional Review Problems