The writing of compare function of qsort function auxiliary function

The fourth argument of Qsort, the compare of the auxiliary function, is the different ways of ordering objects:

First, sort an array of type int

int num[]; int Compare (constvoidconstvoid *b) {  return * (  int *) A-* (int *) b;}

Second, sort the array of char types (same as int type)

Char word[]; int Compare (constvoidconstvoid *b) {  return * (  Char *) A-* (int *) b;}

Third, sort the array of double type

double array[]; int Compare (constvoidconstvoid *b) {  return * (  Double *) a > * (double1 :-1;}

Note the third parameter of Qsort is sizeof (Array[0]).

Iv. sequencing of structural bodies

struct node{    double  data;     int Other ;} node;array[]; int Compare (constvoidconstvoid *b) {      return1 :-1;}

Five, the structure of the two-level ranking

typedefstructnode{intx; inty;} Node; Node array[ -];//Sort by x from small to large, when x is equal by y from largest to smallestintCompareConst void*a,Const void*b) {Node*P1 = (Node *) A; Node*P2 = (Node *) b; if(P1->x! = p2->x)returnP1->x-p2->x; Else        returnP1->y-p2->y;}

Six, sort the string

 typedef struct   node{ int   other;  char  string  [ 100  ];} Node; Node array[ 100  ];  //  by the dictionary order of string Strings in the struct body. int  compare (const  void  * A, const  void  * b) {  return  strcmp ((node *) a)->string , ((node *) b)->string ); 

The writing of compare function of qsort function auxiliary function