如何创建一个让用户知道自己越界的数组？

Question

I'm trying to create a program that helps a user create an array index starting at any integer. It should also notify the user during the execution/accessing the array component that is out-of-bounds.

This is what I have so far.

#include <iostream>
using namespace std;

int main(){
class safeArray;
};

const int CAPACITY=5;

I have set the capacity of the array to 5 so there can be a limit. Leaving the user to be able to go out of bounds.

class safeArray() {
userArray= new int [CAPACITY];

The user will be able to create a new int value for each slot in the array.

cout <<"Enter any integers for your safe userArray:";

if (int=0;i<CAPACITY;i++) {
    cout<<"You are in-bounds!";
}

else (int=0;i>CAPACITY;i++){
    cout<<"You are OUT-OF-BOUNDS!";
    cout<<endl;
    return 0;
};

I went with an if-else statement in order to check the array subscript? I'm new to C++ so any clarification of errors or methods on how to simplify it would be helpful. Thank you.

Answer 1

Your if statements should just read:

if (i<CAPACITY && i>0) {
    cout<<"You are in-bounds!";
}

else if (i>CAPACITY){
    cout<<"You are OUT-OF-BOUNDS!";
    cout<<endl;
    return 0;
};

Also, what happens in the edge case when i == capacity? Your code doesn't handle this case at all.

To make this neater, you could format it with only one if/else statement

if (i<CAPACITY && i>0) { // Or should this be (i<=CAPACITY)??? depends on whether 0 is an index or not
    cout<<"You are in-bounds!";
} else {
    cout<<"You are OUT-OF-BOUNDS!";
    cout<<endl;
    return 0;
};

Answer 2

Instead of handling memory management you could use a standard container such as std::vector for dynamic "arrays" or std::array for fixed size arrays.

std::array has zero overhead on all major compilers and is more or less a C++ wrapper around C arrays.

In order to let the user know when the index is out of bounds most standard containers provide the at(std::size_t n) method (eg std::vector::at ) that do all the rage checking for you and throw a std::out_of_range exception when supplying an invalid index/position.

All you have to do now is catch that exception and print a message if you want to. Here's a little example:

#include <iostream>
#include <array>

int main() {
    std::array<int, 12> arr;
    try {
        std::cout << arr.at(15) << '\n';
    } catch (std::out_of_range const &) {
        std::cout << "Sorry mate, the index you supplied is out of range!" << '\n';
    }
}

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