Why this recursion is infinite?

Question

#include <iostream>
using namespace std;
bool palindromes(char *S, int n, int i){
if (n<=i){
return 1;
}
else{
if (S[i] == S[n-1]){
return palindromes(S,n--,i++);
}
else{ return 0;}
}
}
int main()
{ bool t;
int lung;
char S[100];
cin.getline(S, 100);
lung = cin.gcount() - 1;
cout << "start" << endl;
t=palindromes(S, lung, 0);
if(t==true){
cout<<"the string is palindrome"<<endl;
}else{
cout<<"the string isn't palindrome"<<endl;
}

cout << "end" << endl;
}

Answer 1

You are not decreasing `n`. Change `n--` to `--n`, or better `n-1`.

By the way a good way to debug recursive programs is to just print all the parameters at the top of the function.

Answer 2

The first thing I've noticed is that you pass n-- as argument. So basically n will be passed and decreased afterwords. I think --n would be correct. (also ++i, or to be sure simply write n - 1 and i + 1)

Answer 3

perfect, i’ve understood, the problem was on the decreasing argument, like you told me. now the program works, thanks you