Print all the duplicates in the input string

1.4

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 0.

Solution

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


Output:
s,  count = 2
t,  count = 3


Time Complexity:
O(n)

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