写代码可以在整型有序数组中查找想要的数字，找到了返回下标，找不到返回-1.（折半查找）

代码：

[code]#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>
#include <windows.h>

int binary_search(int arr[], int key, int sz)
{
int left = 0;
int right = sz - 1;
while (left <= right)
{
int mid = (left + right) / 2;
if (arr[mid] == key)
{
return mid;
}
else if (arr[mid] < key)
{
left = mid + 1;
}
else
{
right = mid - 1;
}
}
return -1;
}

int main()
{
int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int key = 0;
printf("\n\n\t\t请输入要查找的数字:");
scanf("%d", &key);
int sz = sizeof(arr) / sizeof(arr[0]);
int ret = binary_search(arr, key, sz);

if (ret == -1)
{
printf("\t\t找不到该数字\n");
}
else
{
printf("\t\t找到了，这个数字的下标是%d\n", ret);
}

system("pause");
return 0;
}

运行界面：