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# Check if a string can be split into two strings with same number of K-frequent characters

• Last Updated : 03 Jun, 2021

Given a string S and an integer K, the task is to check if it is possible to distribute these characters into two strings such that the count of characters having a frequency K in both strings is equal.
If it is possible, then print a sequence consisting of 1 and 2, which denotes which character should be placed in which string. Otherwise, print NO.
Note: One of these new strings can be empty.

Examples:

Input: S = “abbbccc”, K = 1
Output: 1111211
Explanation:
The two strings are “abbbcc” and “c”.
Hence, both the strings have exactly 1 character having frequency K( = 1).

Input: S = “aaaa”, K = 3
Output: 1111
Explanation:
Strings can be split into “aaaa” and “”.
Hence, no character has frequency 3 in both the strings.

Approach:
Follow the steps below to solve the problem:

• Check for the following three conditions to determine if a split is possible or not:
1. If the total number of characters having a frequency K in the initial string is even, then these characters can be placed equally into two strings and the rest of the characters(having a frequency not equal to K) can be placed in any of the two groups.
2. If the total number of characters having a frequency K in the initial string is odd, then if there is a character in the initial string having a frequency greater than K but not equal to 2K, then such a distribution is possible.

Illustration:
S =”abceeee”, K = 1
Split into “abeee” and “ce”. Hence, both the strings have 2 characters with frequency 1.

3. If the total number of characters having a frequency K in the initial string is odd, then if there is a character in the initial string having a                 frequency equal to 2K, then such a distribution is possible.

Illustration:
S =”aaaabbccdde”, K = 2
Split into “aabbc” and “aaddce” so that both the strings have two characters with frequency 2.

• If all the three conditions mentioned above fail, then the answer is “NO”

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the``// above approach``#include ``using` `namespace` `std;` `// Function to print the``// arrangement of characters``void` `DivideString(string s, ``int` `n,``                  ``int` `k)``{``    ``int` `i, c = 0, no = 1;``    ``int` `c1 = 0, c2 = 0;` `    ``// Stores frequency of``    ``// characters``    ``int` `fr = { 0 };` `    ``string ans = ``""``;` `    ``for` `(i = 0; i < n; i++) {``        ``fr[s[i] - ``'a'``]++;``    ``}` `    ``char` `ch, ch1;``    ``for` `(i = 0; i < 26; i++) {` `        ``// Count the character``        ``// having frequency K``        ``if` `(fr[i] == k) {``            ``c++;``        ``}` `        ``// Count the character``        ``// having frequency``        ``// greater than K and``        ``// not equal to 2K``        ``if` `(fr[i] > k``            ``&& fr[i] != 2 * k) {``            ``c1++;``            ``ch = i + ``'a'``;``        ``}` `        ``if` `(fr[i] == 2 * k) {``            ``c2++;``            ``ch1 = i + ``'a'``;``        ``}``    ``}` `    ``for` `(i = 0; i < n; i++)``        ``ans = ans + ``"1"``;` `    ``map<``char``, ``int``> mp;``    ``if` `(c % 2 == 0 || c1 > 0 || c2 > 0) {``        ``for` `(i = 0; i < n; i++) {` `            ``// Case 1``            ``if` `(fr[s[i] - ``'a'``] == k) {``                ``if` `(mp.find(s[i])``                    ``!= mp.end()) {``                    ``ans[i] = ``'2'``;``                ``}``                ``else` `{``                    ``if` `(no <= (c / 2)) {``                        ``ans[i] = ``'2'``;``                        ``no++;``                        ``mp[s[i]] = 1;``                    ``}``                ``}``            ``}``        ``}` `        ``// Case 2``        ``if` `(c % 2 == 1 && c1 > 0) {``            ``no = 1;``            ``for` `(i = 0; i < n; i++) {``                ``if` `(s[i] == ch && no <= k) {` `                    ``ans[i] = ``'2'``;``                    ``no++;``                ``}``            ``}``        ``}` `        ``// Case 3``        ``if` `(c % 2 == 1 && c1 == 0) {``            ``no = 1;``            ``int` `flag = 0;``            ``for` `(``int` `i = 0; i < n; i++) {``                ``if` `(s[i] == ch1 && no <= k) {``                    ``ans[i] = ``'2'``;``                    ``no++;``                ``}``                ``if` `(fr[s[i] - ``'a'``] == k``                    ``&& flag == 0``                    ``&& ans[i] == ``'1'``) {``                    ``ans[i] = ``'2'``;``                    ``flag = 1;``                ``}``            ``}``        ``}` `        ``cout << ans << endl;``    ``}``    ``else` `{``        ``// If all cases fail``        ``cout << ``"NO"` `<< endl;``    ``}``}` `// Driver Code``int` `main()``{` `    ``string S = ``"abbbccc"``;``    ``int` `N = S.size();``    ``int` `K = 1;` `    ``DivideString(S, N, K);` `    ``return` `0;``}`

## Java

 `// Java program for the above problem``import` `java.util.*;` `class` `GFG{``    ` `// Function to print the``// arrangement of characters``public` `static` `void` `DivideString(String s, ``int` `n,``                                          ``int` `k)``{``    ``int` `i, c = ``0``, no = ``1``;``    ``int` `c1 = ``0``, c2 = ``0``;` `    ``// Stores frequency of``    ``// characters``    ``int``[] fr = ``new` `int``[``26``];` `    ``char``[] ans = ``new` `char``[n];` `    ``for``(i = ``0``; i < n; i++)``    ``{``        ``fr[s.charAt(i) - ``'a'``]++;``    ``}` `    ``char` `ch = ``'a'``, ch1 = ``'a'``;``    ``for``(i = ``0``; i < ``26``; i++)``    ``{``        ` `        ``// Count the character``        ``// having frequency K``        ``if` `(fr[i] == k)``        ``{``            ``c++;``        ``}` `        ``// Count the character``        ``// having frequency``        ``// greater than K and``        ``// not equal to 2K``        ``if` `(fr[i] > k && fr[i] != ``2` `* k)``        ``{``            ``c1++;``            ``ch = (``char``)(i + ``'a'``);``        ``}` `        ``if` `(fr[i] == ``2` `* k)``        ``{``            ``c2++;``            ``ch1 = (``char``)(i + ``'a'``);``        ``}``    ``}` `    ``for``(i = ``0``; i < n; i++)``        ``ans[i] = ``'1'``;``    ` `    ``HashMap mp = ``new` `HashMap<>();` `    ``if` `(c % ``2` `== ``0` `|| c1 > ``0` `|| c2 > ``0``)``    ``{``        ``for``(i = ``0``; i < n; i++)``        ``{` `            ``// Case 1``            ``if` `(fr[s.charAt(i) - ``'a'``] == k)``            ``{``                ``if` `(mp.containsKey(s.charAt(i)))``                ``{``                    ``ans[i] = ``'2'``;``                ``}``                ``else``                ``{``                    ``if` `(no <= (c / ``2``))``                    ``{``                        ``ans[i] = ``'2'``;``                        ``no++;``                        ``mp.replace(s.charAt(i), ``1``);``                    ``}``                ``}``            ``}``        ``}` `        ``// Case 2``        ``if` `( (c % ``2` `== ``1``) && (c1 > ``0``) )``        ``{``            ``no = ``1``;``            ``for``(i = ``0``; i < n; i++)``            ``{``                ``if` `(s.charAt(i) == ch && no <= k)``                ``{``                    ``ans[i] = ``'2'``;``                    ``no++;``                ``}``            ``}``        ``}` `        ``// Case 3``        ``if` `(c % ``2` `== ``1` `&& c1 == ``0``)``        ``{``            ``no = ``1``;``            ``int` `flag = ``0``;``            ` `            ``for``(i = ``0``; i < n; i++)``            ``{``                ``if` `(s.charAt(i) == ch1 && no <= k)``                ``{``                    ``ans[i] = ``'2'``;``                    ``no++;``                ``}``                ``if` `(fr[s.charAt(i) - ``'a'``] == k &&``                      ``flag == ``0` `&& ans[i] == ``'1'``)``                ``{``                    ``ans[i] = ``'2'``;``                    ``flag = ``1``;``                ``}``            ``}``        ``}``        ``System.out.println(ans);``    ``}``    ``else``    ``{``        ` `        ``// If all cases fail``        ``System.out.println(``"NO"``);``    ``}``}` `// Driver code``public` `static` `void` `main(String[] args)``{``    ``String S = ``"abbbccc"``;``    ``int` `N = S.length();``    ``int` `K = ``1``;` `    ``DivideString(S, N, K);``}``}` `// This code is contributed by divyeshrabadiya07`

## Python3

 `# Python3 implementation of the``# above approach` `# Function to print the``# arrangement of characters``def` `DivideString(s, n, k):``    ` `    ``c ``=` `0``    ``no ``=` `1``    ``c1 ``=` `0``    ``c2 ``=` `0` `    ``# Stores frequency of``    ``# characters``    ``fr ``=` `[``0``] ``*` `26` `    ``ans ``=` `[]``    ``for` `i ``in` `range``(n):``        ``fr[``ord``(s[i]) ``-` `ord``(``'a'``)] ``+``=` `1` `    ``for` `i ``in` `range``(``26``):` `        ``# Count the character``        ``# having frequency K``        ``if` `(fr[i] ``=``=` `k):``            ``c ``+``=` `1` `        ``# Count the character having``        ``# frequency greater than K and``        ``# not equal to 2K``        ``if` `(fr[i] > k ``and` `fr[i] !``=` `2` `*` `k):``            ``c1 ``+``=` `1``            ``ch ``=` `chr``(``ord``(``'a'``) ``+` `i)` `        ``if` `(fr[i] ``=``=` `2` `*` `k):``            ``c2 ``+``=` `1``            ``ch1 ``=` `chr``(``ord``(``'a'``) ``+` `i)` `    ``for` `i ``in` `range``(n):``        ``ans.append(``"1"``)` `    ``mp ``=` `{}``    ``if` `(c ``%` `2` `=``=` `0` `or` `c1 > ``0` `or` `c2 > ``0``):``        ``for` `i ``in` `range``(n):``            ` `            ``# Case 1``            ``if` `(fr[``ord``(s[i]) ``-` `ord``(``'a'``)] ``=``=` `k):``                ``if` `(s[i] ``in` `mp):``                    ``ans[i] ``=` `'2'` `                ``else``:``                    ``if` `(no <``=` `(c ``/``/` `2``)):``                        ``ans[i] ``=` `'2'``                        ``no ``+``=` `1``                        ``mp[s[i]] ``=` `1``                        ` `        ``# Case 2``        ``if` `(c ``%` `2` `=``=` `1` `and` `c1 > ``0``):``            ``no ``=` `1``            ``for` `i ``in` `range``(n):``                ``if` `(s[i] ``=``=` `ch ``and` `no <``=` `k):``                    ``ans[i] ``=` `'2'``                    ``no ``+``=` `1``                    ` `        ``# Case 3``        ``if` `(c ``%` `2` `=``=` `1` `and` `c1 ``=``=` `0``):``            ``no ``=` `1``            ``flag ``=` `0``            ` `            ``for` `i ``in` `range``(n):``                ``if` `(s[i] ``=``=` `ch1 ``and` `no <``=` `k):``                    ``ans[i] ``=` `'2'``                    ``no ``+``=` `1``                    ` `                ``if` `(fr[s[i] ``-` `'a'``] ``=``=` `k ``and``                              ``flag ``=``=` `0` `and``                            ``ans[i] ``=``=` `'1'``):``                    ``ans[i] ``=` `'2'``                    ``flag ``=` `1` `        ``print``("".join(ans))``    ``else``:``        ` `        ``# If all cases fail``        ``print``(``"NO"``)` `# Driver Code``if` `__name__ ``=``=` `'__main__'``:` `    ``S ``=` `"abbbccc"``    ``N ``=` `len``(S)``    ``K ``=` `1` `    ``DivideString(S, N, K)` `# This code is contributed by mohit kumar 29`

## C#

 `// C# program for the above problem``using` `System;``using` `System.Collections.Generic;` `class` `GFG{``    ` `// Function to print the``// arrangement of characters``public` `static` `void` `DivideString(``string` `s, ``int` `n,``                                          ``int` `k)``{``    ``int` `i, c = 0, no = 1;``    ``int` `c1 = 0, c2 = 0;` `    ``// Stores frequency of``    ``// characters``    ``int``[] fr = ``new` `int``;` `    ``char``[] ans = ``new` `char``[n];` `    ``for``(i = 0; i < n; i++)``    ``{``        ``fr[s[i] - ``'a'``]++;``    ``}` `    ``char` `ch = ``'a'``, ch1 = ``'a'``;``    ``for``(i = 0; i < 26; i++)``    ``{``        ` `        ``// Count the character``        ``// having frequency K``        ``if` `(fr[i] == k)``        ``{``            ``c++;``        ``}` `        ``// Count the character having``        ``// frequency greater than K and``        ``// not equal to 2K``        ``if` `(fr[i] > k && fr[i] != 2 * k)``        ``{``            ``c1++;``            ``ch = (``char``)(i + ``'a'``);``        ``}` `        ``if` `(fr[i] == 2 * k)``        ``{``            ``c2++;``            ``ch1 = (``char``)(i + ``'a'``);``        ``}``    ``}` `    ``for``(i = 0; i < n; i++)``        ``ans[i] = ``'1'``;``    ` `    ``Dictionary<``char``,``               ``int``> mp = ``new` `Dictionary<``char``,``                                        ``int``>();` `    ``if` `(c % 2 == 0 || c1 > 0 || c2 > 0)``    ``{``        ``for``(i = 0; i < n; i++)``        ``{` `            ``// Case 1``            ``if` `(fr[s[i] - ``'a'``] == k)``            ``{``                ``if` `(mp.ContainsKey(s[i]))``                ``{``                    ``ans[i] = ``'2'``;``                ``}``                ``else``                ``{``                    ``if` `(no <= (c / 2))``                    ``{``                        ``ans[i] = ``'2'``;``                        ``no++;``                        ``mp[s[i]] = 1;``                    ``}``                ``}``            ``}``        ``}` `        ``// Case 2``        ``if` `( (c % 2 == 1) && (c1 > 0) )``        ``{``            ``no = 1;``            ``for``(i = 0; i < n; i++)``            ``{``                ``if` `(s[i]== ch && no <= k)``                ``{``                    ``ans[i] = ``'2'``;``                    ``no++;``                ``}``            ``}``        ``}` `        ``// Case 3``        ``if` `(c % 2 == 1 && c1 == 0)``        ``{``            ``no = 1;``            ``int` `flag = 0;``            ` `            ``for``(i = 0; i < n; i++)``            ``{``                ``if` `(s[i] == ch1 && no <= k)``                ``{``                    ``ans[i] = ``'2'``;``                    ``no++;``                ``}``                ``if` `(fr[s[i] - ``'a'``] == k &&``                    ``flag == 0 && ans[i] == ``'1'``)``                ``{``                    ``ans[i] = ``'2'``;``                    ``flag = 1;``                ``}``            ``}``        ``}``        ``Console.Write(ans);``    ``}``    ``else``    ``{``        ` `        ``// If all cases fail``        ``Console.Write(``"NO"``);``    ``}``}` `// Driver code``public` `static` `void` `Main(``string``[] args)``{``    ``string` `S = ``"abbbccc"``;``    ``int` `N = S.Length;``    ``int` `K = 1;` `    ``DivideString(S, N, K);``}``}` `// This code is contributed by rutvik_56`

## Javascript

 ``
Output:
`1111211`

Time Complexity: O(N)
Auxiliary Space: O(N)

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