Print all the duplicates in the input string

Write an efficient C program to print all the duplicates and their counts in the input string

Algorithm: Let input string be “geeksforgeeks”
1: Construct character count array from the input string.

count[‘e’] = 4
count[‘g’] = 2
count[‘k’] = 2
……

2: Print all the indexes from the constructed array which have value greater than 1.

Solution

C++

// C++ program to count all duplicates 
// from string using hashing 
# include <iostream> 
using namespace std; 
# define NO_OF_CHARS 256 
  
class gfg 
{ 
    public : 
      
    /* Fills count array with 
    frequency of characters */
    void fillCharCounts(char *str, int *count) 
    { 
        int i; 
        for (i = 0; *(str + i); i++) 
        count[*(str + i)]++; 
    } 
  
    /* Print duplicates present  
    in the passed string */
    void printDups(char *str) 
    { 
        // Create an array of size 256 and fill 
        // count of every character in it 
        int *count = (int *)calloc(NO_OF_CHARS, sizeof(int)); 
        fillCharCounts(str, count); 
  
        // Print characters having count more than 0 
        int i; 
        for (i = 0; i < NO_OF_CHARS; i++) 
        if(count[i] > 1) 
            printf("%c, count = %d \n", i, count[i]); 
  
        free(count); 
    } 
}; 
  
/* Driver code*/
int main() 
{ 
    gfg g ; 
    char str[] = "test string"; 
    g.printDups(str); 
    //getchar(); 
    return 0; 
} 
  
// This code is contributed by SoM15242 

C

// C program to count all duplicates from string using hashing 
# include <stdio.h> 
# include <stdlib.h> 
# define NO_OF_CHARS 256 
  
/* Fills count array with frequency of characters */
void fillCharCounts(char *str, int *count) 
{ 
   int i; 
   for (i = 0; *(str+i);  i++) 
      count[*(str+i)]++; 
} 
  
/* Print duplicates present in the passed string */
void printDups(char *str) 
{ 
  // Create an array of size 256 and fill count of every character in it 
  int *count = (int *)calloc(NO_OF_CHARS, sizeof(int)); 
  fillCharCounts(str, count); 
  
  // Print characters having count more than 0 
  int i; 
  for (i = 0; i < NO_OF_CHARS; i++) 
    if(count[i] > 1) 
        printf("%c,  count = %d \n", i,  count[i]); 
  
  free(count); 
} 
  
/* Driver program to test to pront printDups*/
int main() 
{ 
    char str[] = "test string"; 
    printDups(str); 
    getchar(); 
    return 0; 
} 

Java

// Java program to count all duplicates from string using hashing 
  
public class GFG  
{ 
    static final int NO_OF_CHARS = 256; 
      
    /* Fills count array with frequency of characters */
    static void fillCharCounts(String str, int[] count) 
    { 
       for (int i = 0; i < str.length();  i++) 
          count[str.charAt(i)]++; 
    } 
       
    /* Print duplicates present in the passed string */
    static void printDups(String str) 
    { 
      // Create an array of size 256 and fill count of every character in it 
      int count[] = new int[NO_OF_CHARS]; 
      fillCharCounts(str, count); 
      
      for (int i = 0; i < NO_OF_CHARS; i++) 
        if(count[i] > 1) 
            System.out.printf("%c,  count = %d \n", i,  count[i]); 
       
    } 
       
    // Driver Method 
    public static void main(String[] args) 
    { 
        String str = "test string"; 
        printDups(str); 
    } 
} 

Python

# Python program to count all duplicates from string using hashing 
NO_OF_CHARS = 256
  
# Fills count array with frequency of characters 
def fillCharCounts(string, count): 
    for i in string: 
        count[ord(i)] += 1
    return count 
  
# Print duplicates present in the passed string 
def printDups(string): 
    # Create an array of size 256 and fill count of every character in it 
    count = [0] * NO_OF_CHARS 
    count = fillCharCounts(string,count) 
  
    # Utility Variable 
    k = 0
  
    # Print characters having count more than 0 
    for i in count: 
        if int(i) > 1: 
            print chr(k) + ", count = " + str(i) 
        k += 1
  
  
  
# Driver program to test the above function 
string = "test string"
print printDups(string) 
  
# This code is contributed by Bhavya Jain 

C#

// C# program to count all duplicates 
// from string using hashing 
using System; 
  
class GFG 
{ 
      
    static int NO_OF_CHARS = 256; 
      
    /* Fills count array with frequency of characters */
    static void fillCharCounts(String str, int[] count) 
    { 
        for (int i = 0; i < str.Length; i++) 
            count[str[i]]++; 
    } 
      
    /* Print duplicates present in 
    the passed string */
    static void printDups(String str) 
    { 
        // Create an array of size 256 and 
        // fill count of every character in it 
        int []count = new int[NO_OF_CHARS]; 
        fillCharCounts(str, count); 
      
        for (int i = 0; i < NO_OF_CHARS; i++) 
            if(count[i] > 1) 
                Console.WriteLine((char)i + ", " + 
                              "count = " + count[i]); 
    } 
      
    // Driver Method 
    public static void Main() 
    { 
        String str = "test string"; 
        printDups(str); 
    } 
} 
  
// This code is contributed by Sam007 

PHP

<?php 
// PHP program to count  
// all duplicates from  
// string using hashing 
function fillCharCounts($str, $count) 
{ 
    for ($i = 0; $i < strlen($str); $i++) 
        $count[ord($str[$i])]++; 
          
    for ($i = 0; $i < 256; $i++) 
        if($count[$i] > 1) 
            echo chr($i) . ", " ."count = " .  
                         ($count[$i]) . "\n"; 
} 
  
// Print duplicates present  
// in the passed string 
function printDups($str) 
{ 
    // Create an array of size  
    // 256 and fill count of  
    // every character in it 
    $count = array(); 
    for ($i = 0; $i < 256; $i++) 
    $count[$i] = 0; 
    fillCharCounts($str, $count); 
  
      
} 
  
// Driver Code 
$str = "test string"; 
printDups($str); 
      
// This code is contributed by Sam007 
?> 

Output :

s,  count = 2
t,  count = 3

Time Complexity : O(n)

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My Personal Notes

C++

C

Java

Python

C#

PHP

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