递归二进制搜索有问题吗? [英] Problem with recursive binary search?

问题描述

为什么我的递归二进制搜索代码不起作用?找不到搜索总是返回元素.

例如:如果有5个元素-4、8、13、17和21.搜索17将返回没有找到的元素.

Why my code for recursive binary search not working? The search always return element is not found.

For example: If there are 5 elements - 4, 8, 13, 17, and 21. Search for 17 return no element found.

#include<iostream>
using namespace std;
int midind, elements, first=0 , last=(elements-1);
int array1[5];
bool searches (int index , int search)
{
	if (index>=elements|| index<=0)
	{
		cout<<"The number "<<search<<" was not found!! \n";
		return false;
	}
	else if (search==array1[index])
	{
		cout<<"The number "<<search<<" was found and its index is "<<index<<" \n";
		return true;
	}
	else if (search>array1[index])
	{
	
		first= index; 
		index= static_cast<int>((first+last)*0.5);
		return searches (index, search);
	
	}
	else if (search<array1[index])
	{
		last = index;
		index = static_cast<int>((first+last)*0.5);
		return searches (index , search);
	}
	
}
void main ()
{
	int i, search;
	cout<<"Enter the number of elements of your integer array  \n";
	cin>>elements;
	cout<<"Enter the "<<elements<<" elements of your integer array in ascending order \n";
	for (i=0 ; i<elements ; i++)
	{
		cin>>array1[i];
	}
	cout<<endl<<"Your integer array is:"<<endl;
	for (i=0 ; i<elements ; i++)
	{
		cout<<array1[i];
		cout<<"\t";
	}
	cout<<endl<<endl;
	cout<<"Enter a number to search for: \n";
	cin>>search;
	midind= static_cast<int>((first+last)*0.5);
	searches (midind , search);
}

推荐答案

7mesho写道:

int midind，elements，first = 0，last =(elements-1);

int midind, elements, first=0 , last=(elements-1);

上面的语句没有任何意义，应该向编译器发出警告.您不能在elements包含任何值之前从elements设置last.

The above statement makes no sense, and should give a compiler warning. You cannot set last from elements before elements contains any value.

您的基本问题似乎是第一个条件:

Your basic problem seems to be the first condition:

if (index>=elements|| index<=0)

第一次运行时，索引始终为< = 0(您自己将其设置为0)

将条件更改为:

In the first run index will always be <= 0 (you set it to 0 yourself)

Change the condition to:

if (index>=elements|| index<0)

但是理查德的观点也是有效的，对谁打败他的人我都会说::thumbsdown:并且:X |

But Richard''s point is also valid and to whoever downvoted him I say: :thumbsdown: and also: X|

谢谢理查德先生！ :)........

Thanks you Mr. Richard! :)........

这篇关于递归二进制搜索有问题吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！