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Palindromic strings of length 3 possible by using characters of a given string

• Last Updated : 03 Aug, 2021

Given a string S consisting of N characters, the task is to print all palindromic strings of length 3 in lexicographical order that can be formed using characters of the given string S.

Examples:

Input: S = “aabc”
Output:
aba
aca

Output:
aba
aca
dbd
dcd
ddd

Approach: The given problem can be solved by using the concept of Hashing, by implementing it using a Map to store count of characters. Follow the steps below to solve the problem:

Below is the implementation of the above approach:

C++

 `// C++ program for the above approach` `#include ``using` `namespace` `std;` `// Function to print all palindromic``// strings of length 3 that can be``// formed using characters of string S``void` `generatePalindrome(string S)``{``    ``// Stores the count of character``    ``unordered_map<``char``, ``int``> Hash;` `    ``// Traverse the string S``    ``for` `(``auto` `ch : S) {``        ``Hash[ch]++;``    ``}` `    ``// Stores all palindromic strings``    ``set st;` `    ``// Iterate over the charchaters``    ``// over the range ['a', 'z']``    ``for` `(``char` `i = ``'a'``; i <= ``'z'``; i++) {` `        ``// If Hash[ch] is equal to 2``        ``if` `(Hash[i] == 2) {` `            ``// Iterate over the characters``            ``// over the range ['a', 'z']``            ``for` `(``char` `j = ``'a'``; j <= ``'z'``; j++) {` `                ``// Stores all the``                ``// palindromic string``                ``string s = ``""``;``                ``if` `(Hash[j] && i != j) {` `                    ``s += i;``                    ``s += j;``                    ``s += i;` `                    ``// Push the s into``                    ``// the set st``                    ``st.insert(s);``                ``}``            ``}``        ``}` `        ``// If Hash[i] is greater than``        ``// or equal to 3``        ``if` `(Hash[i] >= 3) {` `            ``// Iterate over charchaters``            ``// over the range ['a', 'z']``            ``for` `(``char` `j = ``'a'``;``                 ``j <= ``'z'``; j++) {` `                ``// Stores all the``                ``// palindromic string``                ``string s = ``""``;` `                ``// If Hash[j] is positive``                ``if` `(Hash[j]) {``                    ``s += i;``                    ``s += j;``                    ``s += i;` `                    ``// Push s into``                    ``// the set st``                    ``st.insert(s);``                ``}``            ``}``        ``}``    ``}` `    ``// Iterate over the set``    ``for` `(``auto` `ans : st) {``        ``cout << ans << ``"\n"``;``    ``}``}` `// Driver Code``int` `main()``{``    ``string S = ``"ddabdac"``;``    ``generatePalindrome(S);` `    ``return` `0;``}`

Python3

 `# Python3 program for the above approach` `# Function to print all palindromic``# strings of length 3 that can be``# formed using characters of string S``def` `generatePalindrome(S):``    ` `    ``# Stores the count of character``    ``Hash` `=` `{}` `    ``# Traverse the string S``    ``for` `ch ``in` `S:``        ``Hash``[ch] ``=` `Hash``.get(ch,``0``) ``+` `1` `    ``# Stores all palindromic strings``    ``st ``=` `{}` `    ``# Iterate over the charchaters``    ``# over the range ['a', 'z']``    ``for` `i ``in` `range``(``ord``(``'a'``), ``ord``(``'z'``) ``+` `1``):` `        ``# If Hash[ch] is equal to 2``        ``if` `(``chr``(i) ``in` `Hash` `and` `Hash``[``chr``(i)] ``=``=` `2``):``            ` `            ``# Iterate over the characters``            ``# over the range ['a', 'z']``            ``for` `j ``in` `range``(``ord``(``'a'``), ``ord``(``'z'``) ``+` `1``):``                ` `                ``# Stores all the``                ``# palindromic string``                ``s ``=` `""``                ` `                ``if` `(``chr``(j) ``in` `Hash` `and` `i !``=` `j):``                    ``s ``+``=` `chr``(i)``                    ``s ``+``=` `chr``(j)``                    ``s ``+``=` `chr``(i)` `                    ``# Push the s into``                    ``# the set st``                    ``st[s] ``=` `1` `        ``# If Hash[i] is greater than``        ``# or equal to 3``        ``if` `((``chr``(i) ``in` `Hash``) ``and` `Hash``[``chr``(i)] >``=` `3``):``            ` `            ``# Iterate over charchaters``            ``# over the range ['a', 'z']``            ``for` `j ``in` `range``(``ord``(``'a'``), ``ord``(``'z'``) ``+` `1``):` `                ``# Stores all the``                ``# palindromic string``                ``s ``=` `""` `                ``# If Hash[j] is positive``                ``if` `(``chr``(j) ``in` `Hash``):``                    ``s ``+``=` `chr``(i)``                    ``s ``+``=` `chr``(j)``                    ``s ``+``=` `chr``(i)` `                    ``# Push s into``                    ``# the set st``                    ``st[s] ``=` `1` `    ``# Iterate over the set``    ``for` `ans ``in` `st:``        ``print``(ans)` `# Driver Code``if` `__name__ ``=``=` `'__main__'``:``    ` `    ``S ``=` `"ddabdac"``    ` `    ``generatePalindrome(S)` `# This code is contributed by mohit kumar 29`

C#

 `// C# program for the above approach``using` `System;``using` `System.Collections.Generic;` `class` `GFG{`` ` `// Function to print all palindromic``// strings of length 3 that can be``// formed using characters of string S``static` `void` `generatePalindrome(``string` `S)``{``    ` `    ``// Stores the count of character``    ``Dictionary<``char``,``               ``int``> Hash = ``new` `Dictionary<``char``,``                                          ``int``>();` `    ``// Traverse the string S``    ``foreach` `(``char` `ch ``in` `S)``    ``{``        ``if` `(Hash.ContainsKey(ch))``            ``Hash[ch]++;``        ``else``            ``Hash.Add(ch, 1);``    ``}` `    ``// Stores all palindromic strings``    ``HashSet<``string``> st = ``new` `HashSet<``string``>();` `    ``// Iterate over the charchaters``    ``// over the range ['a', 'z']``    ``for``(``char` `i = ``'a'``; i <= ``'z'``; i++)``    ``{``        ` `        ``// If Hash[ch] is equal to 2``        ``if` `(Hash.ContainsKey(i) && Hash[i] == 2)``        ``{``            ` `            ``// Iterate over the characters``            ``// over the range ['a', 'z']``            ``for``(``char` `j = ``'a'``; j <= ``'z'``; j++)``            ``{``                ` `                ``// Stores all the``                ``// palindromic string``                ``string` `s = ``""``;``                ` `                ``if` `(Hash.ContainsKey(j) && i != j)``                ``{``                    ``s += i;``                    ``s += j;``                    ``s += i;` `                    ``// Push the s into``                    ``// the set st``                    ``st.Add(s);``                ``}``            ``}``        ``}` `        ``// If Hash[i] is greater than``        ``// or equal to 3``        ``if` `(Hash.ContainsKey(i) && Hash[i] >= 3)``        ``{``            ` `            ``// Iterate over charchaters``            ``// over the range ['a', 'z']``            ``for``(``char` `j = ``'a'``; j <= ``'z'``; j++)``            ``{``                ` `                ``// Stores all the``                ``// palindromic string``                ``string` `s = ``""``;` `                ``// If Hash[j] is positive``                ``if` `(Hash.ContainsKey(j))``                ``{``                    ``s += i;``                    ``s += j;``                    ``s += i;` `                    ``// Push s into``                    ``// the set st``                    ``st.Add(s);``                ``}``            ``}``        ``}``    ``}` `    ``// Iterate over the set``    ``foreach``(``string` `ans ``in` `st)``    ``{``        ``Console.WriteLine(ans);``    ``}``}` `// Driver Code``public` `static` `void` `Main()``{``    ``string` `S = ``"ddabdac"``;``    ` `    ``generatePalindrome(S);``}``}` `// This code is contributed by SURENDRA_GANGWAR`

Javascript

 ``
Output:
```aba
aca
dbd
dcd
ddd```

Time Complexity: O(26*26)
Auxiliary Space: O(26)

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