Initialize the dynamically allocated array, sizeof Length

When writing a Data Structure experiment today, an array is dynamically allocated:

Bool * vis = new bool [N];

Then initialize the VIS array:

Memset (VIS, 0, sizeof (VIS ));

As a result, the experiment results are always merged.

The cause is eventually discovered:

VIS is a pointer, so the result of sizeof (VIS) is 4. vis only points to the first address of the memory allocated by the heap. It is different from directly opening a static array (I don't know why), and the pointer size occupies 4, therefore, sizeof (VIS) always returns 4 results.

Therefore, the correct method for initializing the Dynamic Allocation array for memset is:

Type * vis = new type [N]; memset (VIS, 0, N * sizeof (type ));

Later, Baidu went to more details: Exploring the differences between C/C ++ array names and pointers

In short, arrays are also a data structure!