折半查找BinarySearch

折半查找的前提是在有序序列里查找。

#include<iostream>
using namespace std;

int BinarySearch(int a[], int size,int x)
{
	int left = 0, right = size-1; 
	while (left <= right)
	{
		int mid =(left + right) / 2;
		if (a[mid] == x)
			return mid;
		else if (a[mid] > x)
			right = mid - 1;
		else left = mid + 1;
	}
	return -1;
}

int main()
{
	int arr[10] = { 1,5,14,18,20,21,45,80,81,100};
	int x;
	cout << "输入要查询的数：";
	cin >> x;
	int result=BinarySearch(arr,10, x);
	if (result == -1)
	{
		cout << "该元素未找到" << endl;
	}
	else cout << "该元素存在且索引为"<<result << endl;
	return 0;

}