Given two string variables, a and b, your task is to write a Java Program to swap these variables without using any temporary or third variable. Use of library methods is allowed.
Examples:
Input: a = "Hello"
b = "World"
Output:
Strings before swap: a = Hello and b = World
Strings after swap: a = World and b = Hello
Method 1 : In order to swap two string variables without using any temporary or third variable, the idea is to use string concatenation and substring() methods to perform this operation. The substring() method comes in two forms, as listed below:
- substring(int beginindex): This function will return the substring of the calling string starting from the index passed as an argument to this function till the last character in the calling string.
- substring(int beginindex, int endindex): This function will return the Substring of the calling string starting from the beginindex(inclusive) and ending at the endindex(exclusive) passed as an argument to this function.
Algorithm:
1) Append second string to first string and
store in first string:
a = a + b
2) call the method substring(int beginindex, int endindex)
by passing beginindex as 0 and endindex as,
a.length() - b.length():
b = substring(0,a.length()-b.length());
3) call the method substring(int beginindex) by passing
b.length() as argument to store the value of initial
b string in a
a = substring(b.length());
Below is the implementation of the above approach:
Java
// Java program to swap two strings without using a temporary// variable.import java.util.*; class Swap{ public static void main(String args[]) { // Declare two strings String a = "Hello"; String b = "World"; // Print String before swapping System.out.println("Strings before swap: a = " + a + " and b = "+b); // append 2nd string to 1st a = a + b; // store initial string a in string b b = a.substring(0,a.length()-b.length()); // store initial string b in string a a = a.substring(b.length()); // print String after swapping System.out.println("Strings after swap: a = " + a + " and b = " + b); } } |
Strings before swap: a = Hello and b = World Strings after swap: a = World and b = Hello
Time Complexity: O(n+m) where n and m are lengths of given strings.
Auxiliary Space: O(n+m)
Method 2 : Using Xor operator
Algorithm :
- Convert the input strings to char arrays.
- The XOR swap algorithm uses the XOR operator to swap the values of two variables without using a temporary variable.
- The program applies this algorithm to each pair of characters in the input string using loop.
- After performing the xor operations convert back the char arrays into strings.
Below is the implementation of the above approach.
Java
/*package whatever //do not write package name here */ import java.io.*;public class Main{ public static void main(String[] args) { String a = "Hello"; String b = "World"; System.out.println("Before swap:"); System.out.println("a = " + a); System.out.println("b = " + b); // Convert strings to char arrays char[] charArrayA = a.toCharArray(); char[] charArrayB = b.toCharArray(); // XOR swap algorithm to swap characters without temporary variable for(int i = 0; i < charArrayA.length && i < charArrayB.length; i++) { charArrayA[i] ^= charArrayB[i]; charArrayB[i] ^= charArrayA[i]; charArrayA[i] ^= charArrayB[i]; } // Convert char arrays back to strings a = new String(charArrayA); b = new String(charArrayB); System.out.println("After swap:"); System.out.println("a = " + a); System.out.println("b = " + b); }} |
Before swap: a = Hello b = World After swap: a = World b = Hello
Time Complexity : O( n+m )
Auxiliary Space : O( n+m )
where n and m are lengths of the string of a and b respectively.
This article is contributed by Harsh Agarwal. If you like Lazyroar and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the Lazyroar main page and help other Geeks. Please write comments if you find anything incorrect or you want to share more information about the topic discussed above.
