#include <iostream>
using namespace std;
string char_to_uppercase(string s, int idx) {
if (idx < 0 || idx > s.length()) return s;
for (int i = 0; i < s.length(); i++) {
if (i == idx && (s[i] >= 'a' && s[i] <= 'z')) {
s[i] -= 32;
}
}
return s;
}
int main() {
string s = "cpp programming";
s = char_to_uppercase(s, 4);
cout << s << endl;
s = char_to_uppercase(s, 0);
cout << s << endl;
s = char_to_uppercase(s, s.length() - 1);
cout << s << endl;
return 0;
}
/*
run:
cpp Programming
Cpp Programming
Cpp ProgramminG
*/