关于二分法查找，也经常称折半查找，思想就是“分而治之”，网上有很多资料，给出
*上的链接（
https://zh.wikipedia.org/wiki/%E6%8A%98%E5%8D%8A%E6%90%9C%E7%B4%A2%E7%AE%97%E6%B3%95
，
http://www.codecodex.com/wiki/Binary_search
），本文不作赘述。下面给出二分查找的非递归和递归的算法。
#include<iostream>
using namespace std;
int search(int *, int, int);
int searchfdg(int *, int, int, int);
int search(int *arra, int key, int high) {
int low = 0;
while (low <= high)
{
int mid = (low + high) / 2;
if (arra[mid] == key) {
return mid;
}else if (arra[mid] > key) {
high = mid - 1;
}else
low = mid + 1;
}
cout << "元素不存在！";
return -1;
}
int searchfdg(int *arra, int key,int low,int high) {
if (low <= high)
{
int mid = (low + high) / 2;
if (key == arra[mid]){
return mid;
}
else if (key < arra[mid]) {
return searchfdg(arra, key, low, mid - 1);
}else if (key > arra[mid])
low = mid + 1;
return searchfdg(arra, key, mid+1,high);
}
else
cout << "元素不存在！";
return -1;
}
int main() {
int arra[] = {3,5,9,14,17,23,29,33,37 };
int size = sizeof(arra) / sizeof(int);
cout << "非递归查找的元素在数组中的位置是：" << endl;
cout << search(arra, 33, size-1) << endl;
cout << "递归查找的元素在数组中的位置是：" << endl;
cout << searchfdg(arra, 33, 0,size-1) << endl; //注意此时的low和high的值
} 运行结果：
