Pfthb

My program should first read an entered string word and then count the amount of repeated letters.

For example, if I enter apple it should print 1, but instead it prints 4.

I suppose word[i] = word[i + 1] isn't the right way to count?

#include<stdio.h>

int main() 

 int i, j, wordLength = 0, alphabeticalSort, counter = 0, swap;
 char word[51];

 scanf("%s", word);

 while (word[wordLength] != '')
 wordLength++;
 

 ...

 for (i = 0; i < wordLength; i++)
 if (word[i] = word[i + 1])
 counter++;
 

 printf("nNumber of repeated letters: %d", counter);

 ...

 return 0;

It's best to split what you're doing into two functions, one of which will count the number of occurrences of each letter.

#define LETTERS 26

/* counts number of occurrences of each lowercase letter in str. Result is placed in outCounts, 
 assuming it has room */
void countletters(char *str, int outCounts)

 memset(outCounts, 0, LETTERS * sizeof (int));

 for (; *str; ++str) 
 if (isupper(*str))
 *str = tolower(str);
 if (islower(*str))
 ++outCounts[*str - 'a'];
 

Then you write another function will examines the outCounts array, which is modified. If a letter is repeated, the corresponding member of this array will be greater than one. I leave this as an exercise to the reader.

You have:

for (i = 0; i < wordLength; i++)
 if (word[i] = word[i + 1])
 counter++;

Look at the 'comparison' inside the loop; you're giving the value of word[i+1] to word[i+1]. This condition will always be true unless the word[i+1]'s value is a 0 or a null char which is also a 0 in the ASCII table.

Remember: the equality operator in C is always ==, so replace the = with ==.

int main()

 char string[80];
 int c = 0, count[26] = 0, x;

 printf("Enter a stringn");
 //gets(string); 
 scanf("%s", string); 
 while (string[c] != '') 

 if (string[c] >= 'a' && string[c] <= 'z') 
 x = string[c] - 'a';
 count[x]++;
 

 c++;
 

 for (c = 0; c < 26; c++)
 printf("%c occurs %d times in the string.n", c + 'a', count[c]);

 return 0;