二分查找的一个重要前提：表中的元素必须有序，且仅限于顺序存储结构。

include <iostream>

using namespace std;

int BinarySearch(int *a, int n, int key);

//注意：表中的元素必须有序，且仅限于顺序存储结构
int BinarySearch(int *a, int n, int key)
{
int low = 0;
int high = n - 1;
while (low <= high)
{
int mid = (low + high) / 2;
if (a[mid] == key)
{
return mid;
}
if (key < a[mid]) //往左区间找
{
high = mid - 1;
}
else //往右区间找
{
low = mid + 1;
}
}

return -1;

}

int main()
{
int a[11] = {5, 16, 20, 27, 30, 36, 44, 55, 60, 67, 71};
int n = 11;

cout << "search 27 = " << BinarySearch(a, n, 27) << endl;
cout << "search 65 = " << BinarySearch(a, n, 65) << endl;
cout << system("pause");
return 0;

}

参考资料：《数据结构（C语言版）》p166-p169