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# Check if two strings can be made equal by swapping one character among each other

Given two strings A and B of length N, the task is to check whether the two strings can be made equal by swapping any character of A with any other character of B only once.
Examples:

Input: A = “SEEKSFORGEEKS”, B = “GEEKSFORGEEKG”
Output: Yes
SEEKSFORGEEKS” and “GEEKSFORGEEKG”

After removing  the elements which are the same and have the same index in both the strings. We have string A=”SS” and B=”GG”.

The new strings are of length two and both the elements in each string are same.Hence swapping is possible.
Input: A = “GEEKSFORGEEKS”, B = “THESUPERBSITE”
Output: No

Brute Force Approach:

1. Initialize a boolean variable flag as false.
2. Iterate through every character in string A and for each character, iterate through every character in string B.
3. For each pair of characters (one from A and one from B), swap the characters and check if the two strings become equal. If they do, set the flag to true and break out of both loops.
4. If the flag is true, print “Yes”, else print “No”.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach``#include ``using` `namespace` `std;` `// Function that returns true if the string``// can be made equal after one swap``bool` `canBeEqual(string a, string b, ``int` `n)``{``    ``bool` `flag = ``false``;``    ``for` `(``int` `i = 0; i < n; i++) {``        ``for` `(``int` `j = 0; j < n; j++) {``            ``swap(a[i], b[j]);``            ``if` `(a == b) {``                ``flag = ``true``;``                ``break``;``            ``}``            ``swap(a[i], b[j]);``        ``}``        ``if` `(flag) ``break``;``    ``}``    ``return` `flag;``}`  `// Driver code``int` `main()``{``    ``string A = ``"SEEKSFORGEEKS"``;``    ``string B = ``"GEEKSFORGEEKG"``;``    ` `    ``if` `(canBeEqual(A, B, A.size()))``        ``printf``(``"Yes"``);``    ``else``        ``printf``(``"No"``);``}`

## Java

 `import` `java.util.*;` `public` `class` `Main {``    ``// Function that returns true if the string can be made equal after one swap``    ``static` `boolean` `canBeEqual(String a, String b, ``int` `n) {``        ``boolean` `flag = ``false``;``        ``for` `(``int` `i = ``0``; i < n; i++) {``            ``for` `(``int` `j = ``0``; j < n; j++) {``                ``char``[] aChars = a.toCharArray();``                ``char``[] bChars = b.toCharArray();``                ``char` `temp = aChars[i];``                ``aChars[i] = bChars[j];``                ``bChars[j] = temp;``                ``a = ``new` `String(aChars);``                ``b = ``new` `String(bChars);``                ``if` `(a.equals(b)) {``                    ``flag = ``true``;``                    ``break``;``                ``}``                ``// Swap back to undo the previous swap``                ``temp = aChars[i];``                ``aChars[i] = bChars[j];``                ``bChars[j] = temp;``                ``a = ``new` `String(aChars);``                ``b = ``new` `String(bChars);``            ``}``            ``if` `(flag) ``break``;``        ``}``        ``return` `flag;``    ``}` `    ``// Driver code``    ``public` `static` `void` `main(String[] args) {``        ``String A = ``"SEEKSFORGEEKS"``;``        ``String B = ``"GEEKSFORGEEKG"``;``        ` `        ``if` `(canBeEqual(A, B, A.length())) {``            ``System.out.println(``"Yes"``);``        ``} ``else` `{``            ``System.out.println(``"No"``);``        ``}``    ``}``}`

## Python3

 `# Python3 implementation of the approach` `# Function that returns true if the string``# can be made equal after one swap``def` `canBeEqual(a, b, n):``    ``flag ``=` `False``    ``for` `i ``in` `range``(n):``        ``for` `j ``in` `range``(n):``            ``a_list ``=` `list``(a)``            ``b_list ``=` `list``(b)``            ``a_list[i], b_list[j] ``=` `b_list[j], a_list[i]``            ``if` `"``".join(a_list) == "``".join(b_list):``                ``flag ``=` `True``                ``break``            ``a_list[i], b_list[j] ``=` `b_list[j], a_list[i]``        ``if` `flag:``            ``break``    ``return` `flag` `# Driver code``if` `__name__ ``=``=` `"__main__"``:``    ``A ``=` `"SEEKSFORGEEKS"``    ``B ``=` `"GEEKSFORGEEKG"` `    ``if` `canBeEqual(A, B, ``len``(A)):``        ``print``(``"Yes"``)``    ``else``:``        ``print``(``"No"``)`

## C#

 `using` `System;` `public` `class` `Program {``    ``// Function that returns true if the string``    ``// can be made equal after one swap``    ``public` `static` `bool` `CanBeEqual(``string` `a, ``string` `b, ``int` `n)``    ``{``        ``bool` `flag = ``false``;``        ``for` `(``int` `i = 0; i < n; i++) {``            ``for` `(``int` `j = 0; j < n; j++) {``                ``char``[] arr1 = a.ToCharArray();``                ``char``[] arr2 = b.ToCharArray();``                ``char` `temp = arr1[i];``                ``arr1[i] = arr2[j];``                ``arr2[j] = temp;``                ``string` `s1 = ``new` `string``(arr1);``                ``string` `s2 = ``new` `string``(arr2);``                ``if` `(s1 == s2) {``                    ``flag = ``true``;``                    ``break``;``                ``}``            ``}``            ``if` `(flag)``                ``break``;``        ``}``        ``return` `flag;``    ``}` `    ``// Driver code``    ``public` `static` `void` `Main()``    ``{``        ``string` `A = ``"SEEKSFORGEEKS"``;``        ``string` `B = ``"GEEKSFORGEEKG"``;``        ``if` `(CanBeEqual(A, B, A.Length)) {``            ``Console.WriteLine(``"Yes"``);``        ``}``        ``else` `{``            ``Console.WriteLine(``"No"``);``        ``}``    ``}``}`

## Javascript

 `// Javascript implementation of the approach` `// Function that returns true if the string``// can be made equal after one swap``function` `canBeEqual(a, b, n) {``    ``let flag = ``false``;``    ``for` `(let i = 0; i < n; i++) {``        ``for` `(let j = 0; j < n; j++) {``            ``let temp = a[i];``            ``a = a.slice(0, i) + b[j] + a.slice(i + 1);``            ``b = b.slice(0, j) + temp + b.slice(j + 1);``            ``if` `(a === b) {``                ``flag = ``true``;``                ``break``;``            ``}``            ``temp = a[i];``            ``a = a.slice(0, i) + b[j] + a.slice(i + 1);``            ``b = b.slice(0, j) + temp + b.slice(j + 1);``        ``}``        ``if` `(flag) ``break``;``    ``}``    ``return` `flag;``}` `// Driver code``let A = ``"SEEKSFORGEEKS"``;``let B = ``"GEEKSFORGEEKG"``;` `if` `(canBeEqual(A, B, A.length))``    ``console.log(``"Yes"``);``else``    ``console.log(``"No"``);`

Output

`Yes`

Time Complexity: O(N^2), where N is the length of the input strings A and B. This is because the code uses two nested loops to try every possible pair of character swaps.

Auxiliary Space: The space complexity of the implementation is O(1), as it uses a constant amount of extra space for variables regardless of the size of the input strings.

Approach: First omit the elements which are the same and have the same index in both the strings. Then if the new strings are of length two and both the elements in each string are the same then only the swap is possible.
Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach``#include ``using` `namespace` `std;` `// Function that returns true if the string``// can be made equal after one swap``bool` `canBeEqual(string a, string b, ``int` `n)``{``    ``// A and B are new a and b``    ``// after we omit the same elements``    ``vector<``char``> A, B;` `    ``// Take only the characters which are``    ``// different in both the strings``    ``// for every pair of indices``    ``for` `(``int` `i = 0; i < n; i++)``    ``{` `        ``// If the current characters differ``        ``if` `(a[i]!= b[i])``        ``{``            ``A.push_back(a[i]);``            ``B.push_back(b[i]);``        ``}``    ``}``    ` `    ``// The strings were already equal``    ``if` `(A.size() == B.size() and``        ``B.size() == 0)``        ``return` `true``;` `    ``// If the lengths of the``    ``// strings are two``    ``if` `(A.size() == B.size() and``        ``B.size() == 2)``    ``{` `        ``// If swapping these characters``        ``// can make the strings equal``        ``if` `(A[0] == A[1] and B[0] == B[1])``            ``return` `true``;``    ``}``    ``return` `false``;``}` `// Driver code``int` `main()``{``    ``string A = ``"SEEKSFORGEEKS"``;``    ``string B = ``"GEEKSFORGEEKG"``;``    ` `    ``if` `(canBeEqual(A, B, A.size()))``        ``printf``(``"Yes"``);``    ``else``        ``printf``(``"No"``);``}` `// This code is contributed by Mohit Kumar`

## Java

 `// Java implementation of the approach``import` `java.util.*;``class` `GFG``{``    ` `// Function that returns true if the string``// can be made equal after one swap``static` `boolean` `canBeEqual(``char` `[]a,``                          ``char` `[]b, ``int` `n)``{``    ``// A and B are new a and b``    ``// after we omit the same elements``    ``Vector A = ``new` `Vector<>();``    ``Vector B = ``new` `Vector<>();` `    ``// Take only the characters which are``    ``// different in both the strings``    ``// for every pair of indices``    ``for` `(``int` `i = ``0``; i < n; i++)``    ``{` `        ``// If the current characters differ``        ``if` `(a[i] != b[i])``        ``{``            ``A.add(a[i]);``            ``B.add(b[i]);``        ``}``    ``}``    ` `    ``// The strings were already equal``    ``if` `(A.size() == B.size() &&``        ``B.size() == ``0``)``        ``return` `true``;` `    ``// If the lengths of the``    ``// strings are two``    ``if` `(A.size() == B.size() &&``        ``B.size() == ``2``)``    ``{` `        ``// If swapping these characters``        ``// can make the strings equal``        ``if` `(A.get(``0``) == A.get(``1``) &&``            ``B.get(``0``) == B.get(``1``))``            ``return` `true``;``    ``}``    ``return` `false``;``}` `// Driver code``public` `static` `void` `main(String[] args)``{``    ``char` `[]A = ``"SEEKSFORGEEKS"``.toCharArray();``    ``char` `[]B = ``"GEEKSFORGEEKG"``.toCharArray();``    ` `    ``if` `(canBeEqual(A, B, A.length))``        ``System.out.printf(``"Yes"``);``    ``else``        ``System.out.printf(``"No"``);``}``}` `// This code is contributed by Rajput-Ji`

## Python3

 `# Python3 implementation of the approach` `# Function that returns true if the string``# can be made equal after one swap``def` `canBeEqual(a, b, n):``    ``# A and B are new a and b``    ``# after we omit the same elements``    ``A ``=``[]``    ``B ``=``[]``    ` `    ``# Take only the characters which are``    ``# different in both the strings``    ``# for every pair of indices``    ``for` `i ``in` `range``(n):``    ` `        ``# If the current characters differ``        ``if` `a[i]!``=` `b[i]:``            ``A.append(a[i])``            ``B.append(b[i])``            ` `    ``# The strings were already equal``    ``if` `len``(A)``=``=` `len``(B)``=``=` `0``:``        ``return` `True``    ` `    ``# If the lengths of the``    ``# strings are two``    ``if` `len``(A)``=``=` `len``(B)``=``=` `2``:``    ` `        ``# If swapping these characters``        ``# can make the strings equal``        ``if` `A[``0``]``=``=` `A[``1``] ``and` `B[``0``]``=``=` `B[``1``]:``            ``return` `True``    ` `    ``return` `False` `# Driver code``A ``=` `'SEEKSFORGEEKS'``B ``=` `'GEEKSFORGEEKG'` `if` `(canBeEqual(A, B, ``len``(A))):``    ``print``(``"Yes"``)``else``:``    ``print``(``"No"``)`

## C#

 `// C# implementation of the above approach``using` `System;``using` `System.Collections.Generic;` `class` `GFG``{``    ` `// Function that returns true if the string``// can be made equal after one swap``static` `Boolean canBeEqual(``char` `[]a,``                          ``char` `[]b, ``int` `n)``{``    ``// A and B are new a and b``    ``// after we omit the same elements``    ``List<``char``> A = ``new` `List<``char``>();``    ``List<``char``> B = ``new` `List<``char``>();` `    ``// Take only the characters which are``    ``// different in both the strings``    ``// for every pair of indices``    ``for` `(``int` `i = 0; i < n; i++)``    ``{` `        ``// If the current characters differ``        ``if` `(a[i] != b[i])``        ``{``            ``A.Add(a[i]);``            ``B.Add(b[i]);``        ``}``    ``}``    ` `    ``// The strings were already equal``    ``if` `(A.Count == B.Count &&``        ``B.Count == 0)``        ``return` `true``;` `    ``// If the lengths of the``    ``// strings are two``    ``if` `(A.Count == B.Count &&``        ``B.Count == 2)``    ``{` `        ``// If swapping these characters``        ``// can make the strings equal``        ``if` `(A[0] == A[1] &&``            ``B[0] == B[1])``            ``return` `true``;``    ``}``    ``return` `false``;``}` `// Driver code``public` `static` `void` `Main(String[] args)``{``    ``char` `[]A = ``"SEEKSFORGEEKS"``.ToCharArray();``    ``char` `[]B = ``"GEEKSFORGEEKG"``.ToCharArray();``    ` `    ``if` `(canBeEqual(A, B, A.Length))``        ``Console.WriteLine(``"Yes"``);``    ``else``        ``Console.WriteLine(``"No"``);``}``}` `// This code is contributed by PrinciRaj1992`

## Javascript

 ``

Output

`Yes`

Time Complexity: O(N), where N is the size of the given strings.

Auxiliary Space: O(N), where N is the size of the given strings.