//在一个有序数组中查找具体的某个数字n。（讲解二分查找）
#include<stdio.h>
int main()
{
	int arr[10] = { 1 ,2, 3, 4, 5, 6, 7,8,9,10 };
	int length = sizeof(arr) / sizeof(arr[0]);
	int left = 0;
	int right = length - 1;
	int mid = 0;
	int i = 0;
	int key = 0;
	printf("请输入要查找的数字：");
	scanf("%d", &key);
	while (left <= right)
	{
		mid = (left + right) / 2;
		if (arr[mid] > key)
		{
			right = mid - 1;
		}
		else if (arr[mid] < key)
		{
			left = mid + 1;
		}
		else
			break;
	}
	if (left <= right)
	{
		printf("找到了，该数字的下标是：%d\n", mid);
	}
	else
	{
		printf("找不到\n");
	}
	return 0;
}


如果实现一个二分查找函数：
int bin_search(int arr[], int left, int right, int key)
{
 int mid = 0;
 while(left<=right)
 {
 mid = (left+right)>>1;
 if(arr[mid]>key)
 {
 right = mid-1;
 }
 else if(arr[mid] < key)
 {
 left = mid+1;
 }
 else
 return mid;//找到了，返回下标
 }
 return -1;//找不到
}