What is the difference between following two snippets?

Question

char *t=new char();

and

char *t=new char[102];

as my code was accepted by using the latter one?

//BISHOPS SPOJ

Answer 1

char *t=new char();

Allocates memory for a single character, and calls the default constructor.

char *t=new char[102];

Creates an array of 102 char s and calls the default constructor.

As the default constructor for POD types is nothing, the difference is the amount of memory allocated (single char vs array of char)

Answer 2

Actually both are pointers on char , but second is pointer to char array.

Which allows you to store 102 characters into the array.

char *t=new char[102];

  0   1   2   3       101
+---+---+---+---+ ... +---+
|   |   |   |         |   |
+---+---+---+---+ ... +---+
  ^
  |
  -----------------------------+---+
                               | * |
                               +---+
                                 t

It allows you to dereference these indexes 0-101.

---

While first one allows you to store only one character.

char *t=new char();
  0
+---+
|   |
+---+
  ^
  |
  -----------------------------+---+
                               | * |
                               +---+
                                 t

Where dereferencing other index than 0 would lead to access outside of bounds and undefined behavior.

---

Deleting

To delete an character char *t=new char();

delete t;

Where to delete an array char *t=new char[102]; you have to write empty brackes, to explicitly say its an array.

delete [] t;

---

Same with these codes

char *t = new char[10];  // Poitner to array of 10 characters

char *t = new char(10);  // Pointer to one character with value of 10

---

Memory initialialization

char *t = new char();      // default initialized (ie nothing happens)
char *t = new char(10);    // zero    initialized (ie set to 0)

Arrays :

char *t = new char[10];   // default initialized (ie nothing happens)
char *t = new char[10](); // zero    initialized (ie all elements set to 0)