#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define GUESTS 30

int compare(const void*, const void*);
int max(int[][GUESTS], int, int);
int main(void) {
srand(time(NULL));
int visits[2][GUESTS] = {0};
int i;
for(i = 0; i < GUESTS; i++) {
visits[0][i] = (double) rand() / RAND_MAX * 24;
visits[1][i] = (double) rand() / RAND_MAX *
(24 - visits[0][i]) + visits[0][i];
}
// 預先排序
    qsort(visits[0], GUESTS, sizeof(int), compare);
qsort(visits[1], GUESTS, sizeof(int), compare);
int t;
for(t = 0; t < 24; t++) {
int num = max(visits, GUESTS, t);
if(num != 0) {
printf("%2d 時訪客數：%2d 位\n", t, num);
}
}
return 0;
}
int compare(const void* a, const void* b) {
return *(int*)a - *(int*)b;
}
int max(int visits[][GUESTS], int count, int time) {
int num, i;
for(num = 0, i = 0; i <= count; i++) {
num = time > visits[0][i] ? num + 1 : num;
num = time > visits[1][i] ? num - 1 : num;
}
return num;
}