这是
个非常经典
排序算法
O(NlogN)阶
#
<stdlib.h>#
<stdio.h>#
<sys/time.h>#
<time.h>#
MAX_LENGTH 100/*Show usage*/
void usage(char * prog)
{
pr
f(\"%s Usage:\\n\", prog);pr
f(\"%s <the count of numbers to sort (should be less than 100)>\\n\", prog);}
/*Generate and initialize the list*/
* generate_list( count){
i; * list;list = (
*)malloc(count*
());
(list 
NULL){
perror(\"malloc\");
NULL;}
/*Initialize the list with
egers less than 100*/srandom((unsigned
)time(NULL));for (i = 0; i < count ; i
)list[i] = random
%100; list;}
/*Show the list*/
void show_list(
* list, length){
i;for(i = 0; i < length; i
)pr
f(\"%d \", list[i]);pr
f(\"\\n\");}
/*algorithm*/
partition( * list, first, last){
left = first; right = last; pivot = list[left];while(left < right)
{
while((right > left) && (list[right] >= pivot))
right --;
(left < right){
list[left] = list[right];
left
;}
while((left < right) && (list[left] < pivot))
left
;(left < right){
list[right] = list[left];
right --;
}
}
list[left] = pivot;
left;}
void quick_sort(
* list, first, last){
(first < last){
split = partition(list, first, last);quick_sort(list, first, split-1);
quick_sort(list, split +1, last);
}
;}
( argc, char * argv
){
length; * list = NULL;struct timeval tpstart,tpend;
float timeuse;
/*Deal with the arguments*/
(argc != 2){
usage(argv[0]);
exit(127);
}
length = atoi(argv[1]);
(!length || length > MAX_LENGTH){
usage(argv[0]);
exit(129);
}
list = generate_list(length);
(list NULL)exit(128);
{
pr
f(\"Soruce list:\\n\");show_list(list, length);
gettimeofday(&tpstart,NULL);
quick_sort(list, 0, length -1);
gettimeofday(&tpend,NULL);
pr
f(\"Ordered list:\\n\");show_list(list, length);
timeuse=1000000*(tpend.tv_sec-tpstart.tv_sec)+ tpend.tv_usec-tpstart.tv_usec;
timeuse/=1000;
pr
f(\"time used: %f msec\\n\", timeuse);}
free(list);
1;}
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