# Minimum swaps to make two strings equal by swapping only with third string

• Last Updated : 14 May, 2021

Given three strings A, B, and C of equal length, the task is to find the minimum number of swap operations that can be performed such that the strings A and B become equal when any swapping can be done only with C.

Examples:

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Input: A = “xyz”, B = “yzx”, C = “yzx”
Output:
Explanation:
Swap all the characters of string C with string A one by one
Input: A = “pqr”, B = “stu”, C = “vwx”
Output: -1
Explanation
It’s impossible to make strings A and B equal, even by using C

Approach: Since the lengths of the strings are equal, the idea is to traverse the strings and check for the characters present in the strings.
For every index ‘i’, the following cases occur:

1. If the character at the given index for the string A is the same as the character in B, then we can proceed to check the next character.
2. If the character at the given index for the string A and B are not equal, then we check if the character at strings B and C or A and C are equal, and accordingly, we swap those characters.
3. If none of the above conditions satisfies, then it’s impossible to make the strings A and B equal.

Below is the implementation of the above approach:

## C++

 `// C++ implementation to find the``// minimum number of swaps to make``// two strings equal` `#include ``using` `namespace` `std;` `// Function to swap the characters``void` `swap(``char``& x, ``char``& y)``{``    ``char` `temp = x;``    ``x = y;``    ``y = temp;``}` `// Function to find the minimum number of swaps``// to make two strings equal``void` `swapOperations(string a, string b, string c)``{``    ``// Counting length of string``    ``int` `l = a.length();``    ``int` `i = 0;` `    ``// Initializing the answer``    ``int` `total_swaps = 0;` `    ``// For loop to iterate through the``    ``// given strings``    ``for` `(i = 0; i < l; i++) {` `        ``// Condition if both character of``        ``// string a and b are equal``        ``if` `(a[i] == b[i])``            ``continue``;` `        ``// Condition if character of``        ``// string a and c are equal``        ``if` `(a[i] == c[i]) {` `            ``// If yes, then swap``            ``// the characters``            ``swap(b[i], c[i]);``            ``total_swaps++;``            ``continue``;``        ``}` `        ``// Condition if character of``        ``// string b and c are equal``        ``if` `(b[i] == c[i]) {` `            ``// If yes, then swap``            ``// the characters``            ``swap(a[i], c[i]);``            ``total_swaps++;``            ``continue``;``        ``}` `        ``// Else, it is impossible to make``        ``// both the strings equal``        ``break``;``    ``}` `    ``// Printing the answer``    ``if` `(i == l)``        ``cout << total_swaps << endl;``    ``else``        ``cout << -1 << endl;``}` `// Driver Code``int` `main()``{``    ``string a = ``"xyz"``;``    ``string b = ``"yzx"``;``    ``string c = ``"yzx"``;` `    ``swapOperations(a, b, c);` `    ``return` `0;``}`

## Java

 `// Java implementation to find the``// minimum number of swaps to make``// two strings equal``class` `GFG {``    ` `    ``// Function to find the minimum number of swaps``    ``// to make two strings equal``    ``static` `void` `swapOperations(``char` `[]a, ``char` `[]b, ``char` `[]c)``    ``{``        ``// Counting length of string``        ``int` `l = a.length;``        ``int` `i = ``0``;``    ` `        ``// Initializing the answer``        ``int` `total_swaps = ``0``;``        ``char` `temp;``    ` `        ``// For loop to iterate through the``        ``// given strings``        ``for` `(i = ``0``; i < l; i++) {``    ` `            ``// Condition if both character of``            ``// string a and b are equal``            ``if` `(a[i] == b[i])``                ``continue``;``    ` `            ``// Condition if character of``            ``// string a and c are equal``            ``if` `(a[i] == c[i]) {``    ` `                ``// If yes, then swap``                ``// the characters``                ``//    swap(b[i], c[i]);``                ``temp = b[i];``                ``b[i] = c[i];``                ``c[i] = temp;``                ` `                ``total_swaps++;``                ``continue``;``            ``}``    ` `            ``// Condition if character of``            ``// string b and c are equal``            ``if` `(b[i] == c[i]) {``    ` `                ``// If yes, then swap``                ``// the characters``                ``//swap(a[i], c[i]);``                ``temp = a[i];``                ``a[i] = c[i];``                ``c[i] = temp;``                ` `                ``total_swaps++;``                ``continue``;``            ``}``    ` `            ``// Else, it is impossible to make``            ``// both the strings equal``            ``break``;``        ``}``    ` `        ``// Printing the answer``        ``if` `(i == l)``                ``System.out.println(total_swaps) ;``        ``else``                ``System.out.println(-``1``) ;``    ``}``    ` `    ``// Driver Code``    ``public` `static` `void` `main (String[] args)``    ``{``        ``String a = ``"xyz"``;``        ``String b = ``"yzx"``;``        ``String c = ``"yzx"``;``    ` `        ``swapOperations(a.toCharArray(), b.toCharArray(), c.toCharArray());``    ` `    ``}``}` `// This code is contributed by Yash_R`

## Python3

 `# Python3 implementation to find the``# minimum number of swaps to make``# two strings equal` `# Function to find the minimum number of swaps``# to make two strings equal``def` `swapOperations(a, b, c) :` `    ``# Counting length of string``    ``l ``=` `len``(a);``    ``i ``=` `0``;` `    ``# Initializing the answer``    ``total_swaps ``=` `0``;` `    ``# For loop to iterate through the``    ``# given strings``    ``for` `i ``in` `range``(l) :` `        ``# Condition if both character of``        ``# string a and b are equal``        ``if` `(a[i] ``=``=` `b[i]) :``            ``continue``;` `        ``# Condition if character of``        ``# string a and c are equal``        ``if` `(a[i] ``=``=` `c[i]) :` `            ``# If yes, then swap``            ``# the characters``            ``#swap(b[i], c[i]);``            ``b[i], c[i] ``=` `c[i], b[i];``            ``total_swaps ``+``=` `1``;``            ``continue``;` `        ``# Condition if character of``        ``# string b and c are equal``        ``if` `(b[i] ``=``=` `c[i]) :` `            ``# If yes, then swap``            ``# the characters``            ``# swap(a[i], c[i]);``            ``a[i], c[i] ``=` `c[i], a[i];``            ``total_swaps ``+``=` `1``;``            ``continue``;` `        ``# Else, it is impossible to make``        ``# both the strings equal``        ``break``;``    ` `    ``i ``+``=` `1``;` `    ``# Printing the answer``    ``if` `(i ``=``=` `l) :``        ``print``(total_swaps) ;``    ``else` `:``        ``print``(``-``1``);` `# Driver Code``if` `__name__ ``=``=` `"__main__"` `:` `    ``a ``=` `"xyz"``;``    ``b ``=` `"yzx"``;``    ``c ``=` `"yzx"``;` `    ``swapOperations(``list``(a), ``list``(b), ``list``(c));` `# This code is contributed by AnkitRai01`

## C#

 `// C# implementation to find the``// minimum number of swaps to make``// two strings equal``using` `System;` `class` `GFG {``    ` `    ``// Function to find the minimum number of swaps``    ``// to make two strings equal``    ``static` `void` `swapOperations(``char` `[]a, ``char` `[]b, ``char` `[]c)``    ``{``        ``// Counting length of string``        ``int` `l = a.Length;``        ``int` `i = 0;``    ` `        ``// Initializing the answer``        ``int` `total_swaps = 0;``        ``char` `temp;``    ` `        ``// For loop to iterate through the``        ``// given strings``        ``for` `(i = 0; i < l; i++) {``    ` `            ``// Condition if both character of``            ``// string a and b are equal``            ``if` `(a[i] == b[i])``                ``continue``;``    ` `            ``// Condition if character of``            ``// string a and c are equal``            ``if` `(a[i] == c[i]) {``    ` `                ``// If yes, then swap``                ``// the characters``                ``//    swap(b[i], c[i]);``                ``temp = b[i];``                ``b[i] = c[i];``                ``c[i] = temp;``                ` `                ``total_swaps++;``                ``continue``;``            ``}``    ` `            ``// Condition if character of``            ``// string b and c are equal``            ``if` `(b[i] == c[i]) {``    ` `                ``// If yes, then swap``                ``// the characters``                ``//swap(a[i], c[i]);``                ``temp = a[i];``                ``a[i] = c[i];``                ``c[i] = temp;``                ` `                ``total_swaps++;``                ``continue``;``            ``}``    ` `            ``// Else, it is impossible to make``            ``// both the strings equal``            ``break``;``        ``}``    ` `        ``// Printing the answer``        ``if` `(i == l)``                ``Console.WriteLine(total_swaps) ;``        ``else``                ``Console.WriteLine(-1) ;``    ``}``    ` `    ``// Driver Code``    ``public` `static` `void` `Main(``string``[] args)``    ``{``        ``string` `a = ``"xyz"``;``        ``string` `b = ``"yzx"``;``        ``string` `c = ``"yzx"``;``    ` `        ``swapOperations(a.ToCharArray(), b.ToCharArray(), c.ToCharArray());``    ` `    ``}``}` `// This code is contributed by Yash_R`

## Javascript

 ``
Output:
`3`

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