Check whether frequency of characters in a string makes Fibonacci Sequence - GeeksforGeeks

26 Nov, 2021
Given a string with lowercase English alphabets. The task is to check whether the frequency of the characters in the string can be arranged as a Fibonacci series. If yes, print “YES”, otherwise print “NO”.Note:  
Frequencies can be arranged in any way to form Fibonacci Series.
The Fibonacci Series starts from 1. That is the series is 1,1,2,3,5,.....
Examples:  
Input : str = "abeeedd"
Output : YES
Frequency of 'a' => 1
Frequency of 'b' => 1
Frequency of 'e' => 3
Frequency of 'd' => 2
These frequencies are first 4 terms of 
Fibonacci series => {1, 1, 2, 3}

Input : str = "dzzddz"
Output : NO
Frequencies are not in Fibonacci series
Approach:  
Store the frequencies of each character of the string in a map. Let the size of the map be after storing frequencies.
Then, make a vector and insert first ‘n’ elements of the Fibonacci series in this vector.
Then, compare each element of the vector with values of the map. If both elements of vector and values of the map are same, print ‘YES’, otherwise print ‘NO’.
Below is the implementation of the above approach: 
C++
Java
Python3
C#
Javascript
// C++ program to check whether frequency of// characters in a string makes// Fibonacci Sequence #include <bits/stdc++.h>using namespace std; // Function to check if the frequencies// are in Fibonacci seriesstring isFibonacci(string s){    // map to store the    // frequencies of character    map<char, int> m;     for (int i = 0; i < s.length(); i++) {        m[s[i]]++;    }     // Vector to store first n    // fibonacci numbers    vector<int> v;     // Get the size of the map    int n = m.size();     // a and b are first and second terms of    // fibonacci series    int a = 1, b = 1;     int c;    v.push_back(a);    v.push_back(b);     // vector v contains elements of fibonacci series    for (int i = 0; i < n - 2; i++) {        v.push_back(a + b);        c = a + b;        a = b;        b = c;    }     int flag = 1;    int i = 0;     // Compare vector elements with values in Map    for (auto itr = m.begin(); itr != m.end(); itr++) {        if (itr->second != v[i]) {            flag = 0;            break;        }         i++;    }     if (flag == 1)        return "YES";    else        return "NO";} // Driver codeint main(){    string s = "abeeedd";     cout << isFibonacci(s);     return 0;}
// Java program to check whether frequency of// characters in a string makes// Fibonacci Sequenceimport java.util.HashMap;import java.util.Vector; class GFG{     // Function to check if the frequencies    // are in Fibonacci series    static String isFibonacci(String s)    {         // map to store the        // frequencies of character        HashMap<Character,                Integer> m = new HashMap<>();        for (int i = 0; i < s.length(); i++)            m.put(s.charAt(i),            m.get(s.charAt(i)) == null ? 1 :            m.get(s.charAt(i)) + 1);         // Vector to store first n        // fibonacci numbers        Vector<Integer> v = new Vector<>();         // Get the size of the map        int n = m.size();         // a and b are first and second terms of        // fibonacci series        int a = 1, b = 1;         int c;        v.add(a);        v.add(b);         // vector v contains elements of        // fibonacci series        for (int i = 0; i < n - 2; i++)        {            v.add(a + b);            c = a + b;            a = b;            b = c;        }         int flag = 1;        int i = 0;         // Compare vector elements with values in Map        for (HashMap.Entry<Character,                           Integer> entry : m.entrySet())        {            if (entry.getValue() != v.elementAt(i))            {                flag = 1;                break;            }             i++;        }                 if (flag == 1)            return "YES";        else            return "NO";    }     // Driver Code    public static void main(String[] args)    {        String s = "abeeedd";        System.out.println(isFibonacci(s));    }} // This code is contributed by// sanjeev2552
# Python3 program to check whether the frequency# of characters in a string make Fibonacci Sequencefrom collections import defaultdict # Function to check if the frequencies# are in Fibonacci seriesdef isFibonacci(s):     # map to store the frequencies of character    m = defaultdict(lambda:0)     for i in range(0, len(s)):        m[s[i]] += 1     # Vector to store first n fibonacci numbers    v = []     # Get the size of the map    n = len(m)     # a and b are first and second    # terms of fibonacci series    a = b = 1     v.append(a)    v.append(b)     # vector v contains elements of    # fibonacci series    for i in range(0, n - 2):        v.append(a + b)        c = a + b        a, b = b, c     flag, i = 1, 0     # Compare vector elements with values in Map    for itr in sorted(m):        if m[itr] != v[i]:            flag = 0            break                 i += 1         if flag == 1:        return "YES"    else:        return "NO" # Driver codeif __name__ == "__main__":     s = "abeeedd"    print(isFibonacci(s)) # This code is contributed by Rituraj Jain
// C# program to check whether frequency of// characters in a string makes// Fibonacci Sequenceusing System;using System.Collections.Generic;                 class GFG{     // Function to check if the frequencies    // are in Fibonacci series    static String isFibonacci(String s)    {         // map to store the        // frequencies of character        int i = 0;        Dictionary<int,                   int> mp = new Dictionary<int,                                            int>();        for (i = 0; i < s.Length; i++)        {            if(mp.ContainsKey(s[i]))            {                var val = mp[s[i]];                mp.Remove(s[i]);                mp.Add(s[i], val + 1);            }            else            {                mp.Add(s[i], 1);            }        }         // List to store first n        // fibonacci numbers        List<int> v = new List<int>();         // Get the size of the map        int n = mp.Count;         // a and b are first and second terms of        // fibonacci series        int a = 1, b = 1;         int c;        v.Add(a);        v.Add(b);         // vector v contains elements of        // fibonacci series        for (i = 0; i < n - 2; i++)        {            v.Add(a + b);            c = a + b;            a = b;            b = c;        }         int flag = 1;                 // Compare vector elements with values in Map        foreach(KeyValuePair<int, int> entry in mp)        {            if (entry.Value != v[i])            {                flag = 1;                break;            }            i++;        }                 if (flag == 1)            return "YES";        else            return "NO";    }     // Driver Code    public static void Main(String[] args)    {        String s = "abeeedd";        Console.WriteLine(isFibonacci(s));    }} // This code is contributed by 29AjayKumar
<script> // Javascript program to check whether frequency of// characters in a string makes// Fibonacci Sequence // Function to check if the frequencies// are in Fibonacci seriesfunction isFibonacci(s){    // map to store the    // frequencies of character    var m = new Map();     for (var i = 0; i < s.length; i++) {         if(m.has(s[i]))        {            m.set(s[i], m.get(s[i]));        }        else        {            m.set(s[i], 1);        }    }     // Vector to store first n    // fibonacci numbers    var v = [];     // Get the size of the map    var n = m.length;     // a and b are first and second terms of    // fibonacci series    var a = 1, b = 1;     var c;    v.push(a);    v.push(b);     // vector v contains elements of fibonacci series    for (var i = 0; i < n - 2; i++) {        v.push(a + b);        c = a + b;        a = b;        b = c;    }     var flag = 1;    var i = 0;     // Compare vector elements with values in Map    m.forEach((value, key) => {        if (value != v[i]) {            flag = 0;        }    });     if (flag == 1)        return "YES";    else        return "NO";} // Driver codevar s = "abeeedd";document.write( isFibonacci(s)); </script>
YES
 
Time Complexity: O(n), where n is the length of the given string.
Auxiliary Space: O(n)
rituraj_jain
sanjeev2552
29AjayKumar
noob2000
samim2000
cpp-map
Fibonacci
frequency-counting
Strings
Strings
Fibonacci
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