[算法导论]在一个数组中寻找最大值和最小值所需要进行比较的次数

数组大小为ArraySize，若ArraySize为偶数，则需要（n-2）/2×3+1次比较；若ArraySize位奇数，则需要(n-1）/2×3次比较。以两个数为一组，首先比较这两个的大小，然后分别与当前最小值和最大值比较。

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define MAX(a, b) ((a) > (b) ? (a) : (b))

#define GetMinAndMax(a, b, minimum, maximum, times) \
({ \
unsigned int arg1 = (a); \
unsigned int arg2 = (b); \
(minimum) = MIN(arg1, arg2); \
(maximum) = MAX(arg1, arg2); \
(times)++; \
printf("time %3d: Compared %3d and %3d\n", times, arg1, arg2); \
})

#define ARRAY_SIZE  99
static int _Array[ARRAY_SIZE];

static void InitArray(void)
{
srand((unsigned int)time(NULL));
for(int i = 0; i < ARRAY_SIZE; i++)
_Array[i] = rand() % (ARRAY_SIZE * 10);

return;
}

static void PrintArray(void)
{
for(int i = 0; i < ARRAY_SIZE; i += 5)
{
printf("%d\t%d\t%d\t%d\t%d\n",
_Array[i], _Array[i + 1], _Array[i + 2], _Array[i + 3], _Array[i + 4]);
}

return;
}

static void Findminimum(void)
{
unsigned int times = 0;
int minimum;
int maximum;
int beginIndex;
int tempMinimum;
int tempMaximum;

if(ARRAY_SIZE % 2 == 0)
{
GetMinAndMax(_Array[0], _Array[1], minimum, maximum, times);
beginIndex = 2;
}
else
{
minimum = maximum = _Array[0];
beginIndex = 1;
}

for(int i = beginIndex; i < ARRAY_SIZE; i += 2)
{
GetMinAndMax(_Array[i], _Array[i + 1], tempMinimum, tempMaximum, times);
GetMinAndMax(minimum, tempMinimum, minimum, tempMinimum, times);
GetMinAndMax(tempMaximum, maximum, tempMaximum, maximum, times);
}
printf("Has compared %d times, and minimum is %d, maximum is %d\n", times, minimum, maximum);
}

int main(int argc, char * argv[])
{
InitArray();
PrintArray();
Findminimum();

return EXIT_SUCCESS;
}