Write an efficient program to print all the duplicates and their counts in the input string
Method 1: Using hashing
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 values greater than 1.
Solution
C++14
// 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.println(( char )(i) + ", count = " + 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), where n = length of the string passed
Space Complexity: O(NO_OF_CHARS)
Note: Hashing involves the use of an array of fixed size each time no matter whatever the string is.
For example, str = “aaaaaaaaaa”.
An array of size 256 is used for str, only 1 block out of total size (256) will be utilized to store the number of occurrences of ‘a’ in str (i.e count[‘a’] = 10).
Rest 256 – 1 = 255 blocks remain unused.
Thus, Space Complexity is potentially high for such cases. So, to avoid any discrepancies and to improve Space Complexity, maps are generally preferred over long-sized arrays.
Method 2: Using Maps
Approach: The approach is the same as discussed in Method 1, but, using a map to store the count.
Solution:
C++
// C++ program to count all duplicates // from string using maps #include <bits/stdc++.h> using namespace std; void printDups(string str) { map< char , int > count; for ( int i = 0; i < str.length(); i++) { count[str[i]]++; } for ( auto it : count) { if (it.second > 1) cout << it.first << ", count = " << it.second << "\n" ; } } /* Driver code*/ int main() { string str = "test string" ; printDups(str); return 0; } // This code is contributed by yashbeersingh42 |
Java
// Java program to count all duplicates // from string using maps import java.util.*; class GFG { static void printDups(String str) { HashMap<Character, Integer> count = new HashMap<>(); /*Store duplicates present in the passed string */ for ( int i = 0 ; i < str.length(); i++) { if (!count.containsKey(str.charAt(i))) count.put(str.charAt(i), 1 ); else count.put(str.charAt(i), count.get(str.charAt(i)) + 1 ); } /*Print duplicates in sorted order*/ for (Map.Entry mapElement : count.entrySet()) { char key = ( char )mapElement.getKey(); int value = (( int )mapElement.getValue()); if (value > 1 ) System.out.println(key + ", count = " + value); } } // Driver code public static void main(String[] args) { String str = "test string" ; printDups(str); } } // This code is contributed by yashbeersingh42 |
Output :
s, count = 2 t, count = 3
Time Complexity: O(N log N), where N = length of the string passed and it generally takes logN time for an element insertion in a map.
Space Complexity: O(K), where K = size of the map (0<=K<=input_string_length).
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
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