Why do these perfectly similiar codes not work? - c++

Question

I'm learning about functions in C++ and I saw this code on Tutorialspoint which tells us whether the
input is an int or a string.
Link to the Tutorialspoint article : https://www.tutorialspoint.com/cplusplus-program-to-check-if-input-is-an-integer-or-a-string
This is the original code:
#include <iostream>
using namespace std;
//check if number or string
bool check_number(string str) {
for (int i = 0; i < str.length(); i++)
if (isdigit(str[i]) == false)
return false;
return true;
}
int main() {
string str = "sunidhi";
if (check_number(str))
cout<<str<< " is an integer"<<endl;
else
cout<<str<< " is a string"<<endl;
string str1 = "1234";
if (check_number(str1))
//output 1
cout<<str1<< " is an integer";
else
//output 2
cout<<str1<< " is a string";
}
The original one works perfectly fine, but my code either only shows ouput 1 or only shows output 2 no matter whether you enter an int or a string.
My code:
Note : my code was written on an online compiler. Link to the compiler : https://www.onlinegdb.com
#include <iostream>
using namespace std;
//the function which checks input
bool check(string s){
for(int i = 0; i < s.length(); i++)
if(isdigit(s[i]) != true)
return false;
return true;
}
//driver code
int main(){
string str = "9760";
if(check(str)){
//output 1
cout<<"Thanks! the word was " <<str;
}
else{
//output 2
cout<<"Oops! maybe you entered a number!";
}
}
Ouput when executing my program : Thanks! the word was 9760
Link to the code project: https://onlinegdb.com/HkcWVpFRU
Thank you!

Answer 1

You are checking if the char is a digit and returning false if it is, you should change it to
bool check(string s){
for(int i = 0; i < s.length(); i++)
if(isdigit(s[i])
return false;
return true;
}
a sidenote, if you want to check for false you can do (!bool) instead of (bool != true) it looks cleaner