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 0.

Solution

• C
• Python

# 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; }

Output:

s,  count = 2
t,  count = 3

Time Complexity: O(n)

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