String array homework - c++

Question

So i have a hw problem for my class where i have to store ten names, capitalize them and then sort them alphabetically. We just started using strings and there are some things that are still a little confusing to me. This code can store all the names in a string array, but the UpperCase seems to not be working. I dont know for sure but i think it is because I have second for loop running cap amount of times, which would be 10. And since not every string will have 10 elements, i'm running into problems?..Is that it or is it something else? Well i tried to fix this by using the .length (function?), to find the length of each name in the array, but I always get errors. Any help is appreciated, thanks!
#include<iostream>
#include<string>
using namespace std;
void UpperCase(string names[],int cap);
void print(string names[],int cap);
void swap(string names[],int &x,int &y);
string names[10];
int main(){
char a;
cout<<sizeof(a);
for(int i=0;i<10;i++){
cout<<"Enter a name for student "<<i+1<<" : ";
cin>>names[i];
cout<<endl;
}
UpperCase(names,10);
cout<<endl;
print(names,10);
cout<<endl;
print(names,10);
return 0;
}
void print(string names[],int cap){
for(int i=0;i<cap;i++)
cout<<names[i]<<endl;
}
void UpperCase(string names[],int cap){
for(int student=0;student<cap;student++){
for(int letter=0;letter<names[student].length();letter++){
if(names[student][letter]>='a')
names[student][letter]-=('a'-'A');
}
}
}

Answer 1

Your inner loop should be iterating for the length of the string. string::length() is a function, not a field, so you need the parentheses. There's also a standard library function for converting a character to upper case.
#include <cctype>
using std::toupper;
void UpperCase(string names[],int cap){
for(int student=0;student<cap;student++){
for(int letter=0;letter<names[student].length();letter++){
names[student][letter] = toupper(names[student][letter]);
}
}
}

Answer 2

..., but the UpperCase seems to not be working
So write a minimal program that just calls UpperCase on known input. It makes it easy to debug, and would also make a much better question. We don't need to see the print or swap to help with that, and prompting the user for input isn't relevant to whether UpperCase works or not.
Having said that, you should use std::string::length() - however, you say
Well i tried to fix this by using the .length (function?), to find the length of each name in the array, but I always get errors
but don't show what you actually tried, or what the errors were.
Here's a minimal, complete and self-contained program, using std::toupper as per T.C.'s answer. I changed it to demonstrate more modern style, and to show there are easier ways to confirm your functions work than to write a whole program and then find out it's broken.
#include <algorithm> // for transform, for_each
#include <cctype> // for toupper
#include <string>
#include <vector> // easier to use (correctly) than bare arrays
// change a string to upper case
void str_toupper(std::string &s) {
std::transform(s.begin(), s.end(),
s.begin(),
[](char c) -> char { return std::toupper(c); });
}
// change a vector of strings to upper case
void vec_toupper(std::vector<std::string>& v) {
std::for_each(v.begin(), v.end(), str_toupper);
}
using namespace std;
int main() {
vector<string> const input = { "bob", "alice cooper", "Eve" };
vector<string> const expected = { "BOB", "ALICE COOPER", "EVE" };
vector<string> working = input;
vec_toupper(working);
return working == expected ? 0 : -1;
// use cout or debugger to solve problem only if program returns nonzero
}