Character Counting in a String - C program -

i have written c program. it's character counting program. give input below

input: abcappprc
, need output: a2b1c2p3r1.

but gives output a2b1c2a1p3p2p1r1c1. doing per logic have written in program. don't want count characters of string have been counted. can suggest logic should implement this?

#include <stdio.h>  int main() {         char str[30]= "abcappprc";         char stroutput[60]="";         char *ptr= &str, *ptr2=&str;         char ch='a';         int count=0;         puts(str);          while (*ptr !=null)         {                 count =0;                 ch = *ptr;                 while (*ptr2!= null)                 {                         if (*ptr2 == ch) count++;                         ptr2++;                 }                 printf("%c%d",*ptr, count);                 ptr++;                 ptr2 = ptr;         } } 

you need separate counting printing.

1. the first loop goes through input , counts number of occurrences of each character, storing counts in array indexed character code.
2. the second loop goes through array of counts , prints character corresponding non-zero count followed count.

for example:

#include <stdio.h>  int main(void) {     char str[] = "abcappprc";     int counts[256] = { 0 };      puts(str);      (char *ptr = str; *ptr != '\0'; ptr++)         counts[(unsigned char)*ptr]++;     (int = 0; < 256; i++)     {         if (counts[i] != 0)             printf("%c%d", i, counts[i]);     }     putchar('\n');     return(0); } 

sample output:

abcappprc a2b1c2p3r1 

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i not understand first for loop. please explain it?

the for control line steps through string str 1 character @ time. for loop equivalent of outer while loop in original code.

char *ptr = str; ... while (*ptr != '\0') {     ...     ptr++; } 

the body of loop converts *ptr (a plain char) unsigned char (so guaranteed positive), , uses value index array counts. thus, example, on first iteration, a mapped 65, , counts[65] incremented. thus, each character code, loop increments count corresponding character code each time character encountered in string.

the second loop picks out non-zero counts, printing character code character followed count.

(incidentally, should have been getting compilation warning original char *ptr = &str type mismatch between char * , char (*)[30]. learn when put ampersands in front of array names — seldom unless there subscript after array name. thus, &array — not — wrong; contrast, &array[0] valid. note on machines, null defined ((void *)0) , elicits warning when compare plain char, did while (*ptr != null). should compare characters '\0' in rewrite; should reserve null use pointers.)