count letters in a string c++ - c++

Question

I am trying to write a function that counts the number of characters in a string excluding spaces. However, the output is always wrong so there is something wrong with my code.
There is something wrong with my code but I can't figure it out. Please help me with my programming homework.
#include <iostream>
#include <bits/stdc++.h>
#include <stdio.h>
#include <ctype.h>
using namespace std;
int countLetters (char s[], int size_s){
int isLetter = 0;
for(int i =0; i<size_s;i++){
if (isalpha(s[i])){
isLetter ++;
}
}
return isLetter;
}
int main (){
char s[100];
gets(s);
int n = sizeof(s)/sizeof(s[0]);
cout << countLetters(s,n);
}
Here is an example of the wrong output:
hi
10
PS C:\Users\user\OneDrive\Desktop\cpp practical> cd "c:\Users\user\OneDrive\Desktop\cpp practical\" ; if ($?)
{ g++ count_letters.cpp -o count_letters } ; if ($?) { .\count_letters }
hi
6
PS C:\Users\user\OneDrive\Desktop\cpp practical> cd "c:\Users\user\OneDrive\Desktop\cpp practical\" ; if ($?)
{ g++ count_letters.cpp -o count_letters } ; if ($?) { .\count_letters }
hi
10
PS C:\Users\user\OneDrive\Desktop\cpp practical>

Answer 1

To begin with, I think your information source, like PepijnKramer, said in the comments, is a bit old. There are much easier data types you can use to complete this problem like std::string below.
First of all, your code is redundant in its header files: #include <bits/stdc++.h> is a nonstandard header, and you already have all the libraries you need.
Secondly, your main problem comes from the lines
char s[100];
gets(s);
int n = sizeof(s)/sizeof(s[0]);
You see, you first create a char array called s with 100 elements. However, you never give them an initial value, so the random garbage that came with the initialization stays. However, C++ also does not reset the values, so some of them may be randomized into letters. Then, you just use gets() to input the string. However, gets() only fills the array s with the number of characters you entered. Therefore, if you do not enter 100 characters, the random garbage that still can be a letter remains. Finally, when you do the size with the integer n, it turns out the result is always 100 because you defined s to have 100 elements, so when you run the function, you still iterate over the garbage in the array s. Therefore, depending on chance of what the garbage includes, your output is incorrect. To solve this, you can either you make sure to initialize it by
char s[100] = { };
Or switch a datatype. Here is a correct solution using std::string:
#include <bits/stdc++.h>
using namespace std;
int countLetters (string a, int size_s){
int isLetter = 0;
for (int i = 0; i < size_s; i++) {
if (isalpha(a[i])){
isLetter++;
}
}
return isLetter;
}
int main () {
string s;
getline(cin, s);
cout << countLetters(s, s.length());
}