Java Program to Swap two Strings Without Using any Third Variable
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.
Input: a = "Hello" b = "World" Output: Strings before swap: a = Hello and b = World Strings after swap: a = World and b = Hello
Method: 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.
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:
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)
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