二分查找（折半查找）

#include<stdio.h>
int binary_search(int arr[],int left,int right,int key)
{
while (left <= right)
{
int mid = (left + right) / 2;
if (key > arr[mid])
{
left = mid + 1;
}
else if (key < arr[mid])
{
right = mid - 1;
}
else
{
return mid;
}
}
if (left > right)
{
return -1;
}
return 0;
}
int main()
{
int key = 100;
scanf("%d", &key);
int arr[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int left = 0;
int right = sizeof(arr) / sizeof(arr[0]) - 1;
int temp = binary_search(arr, left, right, key);
if (temp == -1)
{
printf("没找到\n");
}
else
{
printf("是第%d 位\n", temp);
}
return 0;
}