一、对int类型数组排序
int num[100];
Sample:
int cmp ( const void *a , const void *b )
{
return *(int *)a - *(int *)b;
}
qsort(num,100,sizeof(num[0]),cmp);
二、对char类型数组排序（同int类型）
char word[100];
Sample:
int cmp( const void *a , const void *b )
{
return *(char *)a - *(int *)b;
}
qsort(word,100,sizeof(word[0]),cmp);
三、对double类型数组排序（特别要注意）
double in[100];
int cmp( const void *a , const void *b )
{
return *(double *)a > *(double *)b ? 1 : -1;
}
qsort(in,100,sizeof(in[0]),cmp)；
四、对结构体一级排序
struct In
{
double data;
int other;
}s[100]
//按照data的值从小到大将结构体排序,关于结构体内的排序关键数据data的类型可以很多种，参考上面的例子写
int cmp( const void *a ,const void *b)
{
return ((In *)a)->data > ((In *)b)->data ? 1 : -1;
}
qsort(s,100,sizeof(s[0]),cmp);
五、对结构体二级排序
struct In
{
int x;
int y;
}s[100];
//按照x从小到大排序，当x相等时按照y从大到小排序
int cmp( const void *a , const void *b )
{
struct In *c = (In *)a;
struct In *d = (In *)b;
if(c->x != d->x) return c->x - d->x;
else return d->y - c->y;
}
qsort(s,100,sizeof(s[0]),cmp);
六、对字符串进行排序
struct In
{
int data;
char str[100];
}s[100];
//按照结构体中字符串str的字典顺序排序
int cmp ( const void *a , const void *b )
{
return strcmp( (*(In *)a)->str , (*(In *)b)->str );
}
qsort(s,100,sizeof(s[0]),cmp);
功 能: 使用快速排序例程进行排序
用 法: void qsort(void *base, int nelem, int width, int (*fcmp)(const void *,const void *));
各参数：1 待排序数组首地址 2 数组中待排序元素数量 3 各元素的占用空间大小 4 指向函数的指针，用于确定排序的顺序
程序例:
#include <iostream>
using namespace std;
#include <stdlib.h>
#include <string.h>
int compare( const void *a, const void *b);
char * list[5]= {"cat","car","cab","cap","can"};
int main()
pascal 例程
program quicksort;
const
{$ifndef MACOS}
max = 100000;
{$else}
max = 1000; {Actually it works with 100000 also, but that might }
{lead problems occacionally.}
{$endif}
type
tlist = array[1..max] of longint;
var
data : tlist;
procedure qsort(var a : tlist);
procedure sort(l,r: longint);
var
i,j,x,y: longint;
begin
i:=l;
j:=r;
x:=a[(l+r) div 2];
repeat
while a
<x do
inc(i);
while x<a[j] do
dec(j);
if not(i>j) then
begin
y:=a;
a:=a[j];
a[j]:=y;
inc(i);
j:=j-1;
end;
until i>j;
if l<j then
sort(l,j);
if i<r then
sort(i,r);
end;
begin
sort(1,max);
end;
var
i : longint;
begin
write('Creating ',Max,' random numbers between 1 and 500000');
randomize;
for i:=1 to max do
data:=random(500000);
writeln;
writeln('Sorting...');
qsort(data);
writeln;
for i:=1 to max do
begin
write(data:7);
if (i mod 10)=0 then
writeln;
end;
end.
{
int x;
qsort((void *)list,5,sizeof(list[0]),compare);
for (x=0;x<5;x++)
cout<<list[x]<<endl;
return 0;
}
int compare(const void *a,const void *b)
{
return(strcmp(*(char**)a,*(char**)b));
}