Count words that appear exactly two times in an array of words

Given an array of n words. Some words are repeated twice, we need count such words.
Examples:

Input : s[] = {"hate", "love", "peace", "love", 
               "peace", "hate", "love", "peace", 
               "love", "peace"};
Output : 1
There is only one word "hate" that appears twice

Input : s[] = {"Om", "Om", "Shankar", "Tripathi", 
                "Tom", "Jerry", "Jerry"};
Output : 2
There are two words "Om" and "Jerry" that appear
twice.

Source : Amazon Interview



  1. Traverse the given array, store counts of words in a hash table
  2. Traverse hash table and count all words with count 2.

Below is the implementation.

C++

filter_none

edit
close

play_arrow

link
brightness_4
code

// C++ program to count all words with count
// exavtly 2.
#include <bits/stdc++.h>
using namespace std;
  
// Returns count of words with frequency
// exactly 2.
int countWords(string str[], int n)
{
    unordered_map<string, int> m;
    for (int i = 0; i < n; i++)
        m[str[i]] += 1;
  
    int res = 0;
    for (auto it = m.begin(); it != m.end(); it++)
        if ((it->second == 2))
            res++;
  
    return res;
}
  
// Driver code
int main()
{
    string s[] = { "hate", "love", "peace", "love",
                   "peace", "hate", "love", "peace",
                   "love", "peace" };
    int n = sizeof(s) / sizeof(s[0]);
    cout << countWords(s, n);
    return 0;
}

chevron_right






                        filter_none









Java














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















// Java program to count all words with count 


// exactly 2. 


import java.util.HashMap; 


import java.util.Map; 


public class GFG { 


       


    // Returns count of words with frequency 


    // exactly 2. 


    static int countWords(String str[], int n) 


    { 


        // map to store count of each word 


        HashMap<String, Integer> m = new HashMap<>(); 


          


        for (int i = 0; i < n; i++){ 


            if(m.containsKey(str[i])){ 


                int get = m.get(str[i]); 


                m.put(str[i], get + 1); 


            } 


            else{ 


                m.put(str[i], 1); 


            } 


        } 


              


        int res = 0; 


        for (Map.Entry<String, Integer> it: m.entrySet()){ 


            if(it.getValue() == 2) 


                res++; 


        } 


                  


        return res; 


    } 


       


    // Driver code 


    public static void main(String args[]) 


    { 


        String s[] = { "hate", "love", "peace", "love", 


                       "peace", "hate", "love", "peace", 


                       "love", "peace" }; 


        int n = s.length; 


        System.out.println( countWords(s, n)); 


    } 


} 


// This code is contributed by Sumit Ghosh 



















                        chevron_right







                        filter_none









Python3














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















# Python program to count all 


# words with count 


# exactly 2. 


   


# Returns count of words with frequency 


# exactly 2. 


def countWords(stri, n): 


    m = dict() 


    for i in range(n): 


        m[stri[i]] = m.get(stri[i],0) + 1


   


    res = 0


    for i in m.values(): 


        if i == 2: 


            res += 1


   


    return res 


   


# Driver code 


s = [ "hate", "love", "peace", "love", 


      "peace", "hate", "love", "peace", 


                "love", "peace" ] 


n = len(s) 


print(countWords(s, n)) 


  


# This code is contributed 


# by Shubham Rana 



















                        chevron_right







                        filter_none









C#














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















// C# program to count all words with count 


// exactly 2. 


using System; 


using System.Collections.Generic; 


  


class GFG  


{ 


      


    // Returns count of words with frequency 


    // exactly 2. 


    static int countWords(String []str, int n) 


    { 


        // map to store count of each word 


        Dictionary<String,int> m = new Dictionary<String,int>(); 


          


        for (int i = 0; i < n; i++) 


        { 


            if(m.ContainsKey(str[i])) 


            { 


                int get = m[str[i]]; 


                m.Remove(str[i]); 


                m.Add(str[i], get + 1); 


            } 


            else


            { 


                m.Add(str[i], 1); 


            } 


        } 


              


        int res = 0; 


        foreach(KeyValuePair<String, int> it in m) 


        { 


            if(it.Value == 2) 


                res++; 


        } 


                  


        return res; 


    } 


      


    // Driver code 


    public static void Main(String []args) 


    { 


        String []a = { "hate", "love", "peace", "love", 


                    "peace", "hate", "love", "peace", 


                    "love", "peace" }; 


        int n = a.Length; 


        Console.WriteLine( countWords(a, n)); 


    } 


} 


  


// This code is contributed by Rajput-Ji 



















                        chevron_right







                        filter_none










Output:


1



This article is contributed by Saumya Tiwari. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.


Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.



          
          
          

          

    

        My Personal Notes
        arrow_drop_up
    

    

        
        

            
            
        

    


Recommended Posts:

Improved By :  Rajput-Ji