Qsort/sort-C + + calls the CMP function to sort character array

This problem repeatedly met and forgot how to do once again, this time intends to thoroughly understand.

· C

The first order of the so-called character array should be the sort (char) *a[] array instead of (char) a[][], which cannot be directly called Qsort to implement its ordering.

CMP function notation:

1 int cmp (constvoidconstvoid *b) {2     return strcmp (* ((char* *) a), * ((char* *) b)); 3 }

It is easy to imagine that a string was assigned a specific storage space at initialization time, and we identified the string with its first address.

The ordering of the character array is actually the sort of the variable type: the character pointer (char*).

The result of the sort is actually a change in the position of the (character) pointer array element.

Therefore, the CMP function provides an interface to a const void pointer that represents the sorted object.

We're going to sort of *a, *b (type void), because what we're going to do is sort the strings (character pointers).

First, it is coerced into a pointer to a character pointer, which is equivalent to applying a pointer to the character p, and then A to P.

Then there is *a = P, which indirectly leads to a char type pointer to the corresponding string.

It is also possible to sort *a and *b with the strcmp function by comparing the original string.

The Qsort function:

1 sizeof (Char*), CMP);

· C++

C + + is easier to sort.

Sort function:

1 sort (A, a + N, CMP);

CMP functions:

1 BOOL CMP (charChar *b) {2     return0; 3 }

Because the interfaces provided by the CMP functions in C + + sort are directly oriented to the ordering of elements, we only need to consider the comparison of the character pointers themselves.

Qsort/sort-C + + calls the CMP function to sort character array