#include<iostream>
using namespace std;
template<typename T>
class List
{
public:
    T *values;
    int capacity;
    int counter;
public:
    List()
    {
        values = NULL;
        capacity = 0;
        counter = 0;
    }
    List(int cap)
    {
        capacity = cap;
        values = new T[cap];
        counter = 0;
    }
    bool insert(T item)
    {
        if (isFull() == false)
        {
            values[counter] = item;
            counter  ;
            return true;
        }
        return false;
    }
    bool insertAt(T item, int index)
    {
        
        if (isFull() == false && index < counter)
        {
            capacity  ;
            for (int i = capacity; i > index; i--)
                values[i] = values[i - 1];
            
            values[index] = item;
            
            return true;
        }
        return false;
    }
    bool isFull()
    {
        if (counter == capacity)
        {
            return true;
        }
        return false;
    }
    void print()
    {
        for (int i = 0; i < capacity; i  )
        {
            cout << values[i] << " ";
        }
    }
    
};
int main()
{
    List<int> obj1(5);
    obj1.insert(1); //0
    obj1.insert(2); //1
    obj1.insert(3); //2
    obj1.insert(4); //3
    
    obj1.insertAt(3, 1);
    obj1.values[1];
    obj1.print();
    
}

Kindly look into this program I have to insert an element at given position. But when I run this program I am getting garbage at the end element of an array. Kindly check and let me know where is the problem? Please check the insertAt function I think this function has some logical error. I have added the main function when I call print function it give garbage at the last index

CodePudding user response：

bool insertAt(T item, int index)
    {
        
    
        if (!isFull() && index < counter)
        {
            for (int i = counter; i > index; i--) {
                values[i] = values[i - 1];
            }
            values[index] = item;
            counter  ;
            return true;
        }
        return false;
    }

void print()
    {
        for (int i = 0; i < counter; i  )
        {
            cout << values[i] << " ";
        }
    }

I have corrected these two function. Try these functions instead of the one you implemented

CodePudding user response：

There are a few issues with your insertAt function:

1. You need to increase counter, not capacity. Your capacity is fixed at construction time. It cannot change without allocating a new underlying array and copying the elements over.
2. You also should only run your loop from counter to index rather than starting at capacity, since the elements between counter and capacity will be uninitialized assuming T is a trivial type.
3. You shouldn't set values[index] = item until after the loop has finished moving all of the existing items.
4. You should return true after the loop, and return false outside the if block

bool insertAt(T item, int index)
{
    if (!isFull() && index < counter)
    {
        for (int i = counter; i > index; i--) {
            values[i] = values[i - 1];    
        }
        values[index] = item;
        counter  ;
        return true;
    }
    return false;
}

Note: You have a similar mistake in your print function. You're printing all of the values up to capacity, but the ones between counter and capacity are uninitialized. That loop should also terminate at counter.

Demo

It's also worth pointing out that you never delete[] values, so that memory will leak when your list object dies. You also haven't followed the rule of three though, so if you add a destructor that delete[]s values you'll also need a copy-constructor and copy-assignment operator that copy the underlying array so that multiple list objects don't try to delete[] the same array.