二分查找

算法代码：

#include<stdio.h>
int binary_search(int*arr, int keynumber, int size)
{
int left = 0, right = size - 1;
int mid;
while (left <= right)
{
mid = (left + right) >> 1;//求两一处个数的平均值，这样写的目的是为了防止溢出
if (keynumber < arr[mid])
{
right = mid - 1;
}
else if (keynumber>arr[mid])
{
left = mid + 1;
}
else
{
return mid;
}
}
return -1;


}
int main()
{
int s, keynumber = 0; 
int arr[] = { 0, 1, 2, 3, 4, 5, 6 };
int size = sizeof(arr) / sizeof(arr[0]);
s = binary_search(arr, 3, size);
printf("%d", s);
return 0;


}