# C语言经典算法 - 二分搜寻法（搜寻原则的代表）

```#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define MAX 10
#define SWAP(x,y) {int t; t = x; x = y; y = t;}
void quicksort(int[], int, int);
int bisearch(int[], int);
int main(void)
{
int number[MAX] =  { 0  };
int i, find;
srand(time(NULL));
for (i = 0; i < MAX; i++)
{
number[i] = rand() % 100;
}
quicksort(number, 0, MAX - 1);
printf("数列：");
for (i = 0; i < MAX; i++)
printf("%d ", number[i]);
printf("\n输入寻找对象：");
scanf("%d", &find);
if ((i = bisearch(number, find)) >= 0)
printf("找到数字于索引%d ", i);
else
printf("\n找不到指定数");
printf("\n");
return 0;
}

int bisearch(int number[], int find)
{
int low, mid, upper;
low = 0;
upper = MAX - 1;
while (low <= upper)
{
mid = (low + upper) / 2;
if (number[mid] < find)
low = mid + 1;
else if (number[mid] > find)
upper = mid - 1;
else
return mid;
}
return  - 1;
}

void quicksort(int number[], int left, int right)
{
int i, j, k, s;
if (left < right)
{
s = number[(left + right) / 2];
i = left - 1;
j = right + 1;
while (1)
{
while (number[++i] < s)
;
// 向右找
while (number[--j] > s)
;
// 向左找
if (i >= j)
break;
SWAP(number[i], number[j]);
}
quicksort(number, left, i - 1); // 对左边进行递回
quicksort(number, j + 1, right); // 对右边进行递回
}
}

```

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