二分查找的递归和非递归实现

/*

author:justinzhang

email:uestczhangchao@gmail.com

time:2012-8-3018:54:01

desc:binarysearchfromtheaocpp380

*/

#include<iostream>

#include<vector>

#include<memory>//forauto_ptr,butauto_ptrdoesnotsupportarrays

#include<ctime>//fortime(0)function

#include<cstdlib>//forsrandandrandfunction

#include<algorithm>//forsortandbinary_searchfunction

usingnamespacestd;

template<classtype>

typerandom(typestart,typeend)

{

srand((int)time(0)*rand());

return(start+(end-start)*rand()/(RAND_MAX+1.0));

}

template<classtype>boolmy_binary_search(vector<type>data,intbegin,intend,typevalue)

{

intL=begin;

intU=end;

while(U>L)//注意此处不要写成了U>=L,如果是>=，并且数组下标从0开始的话，就会导致vector下标越界

{

intM=L+(U-L)/2;

if(data[M]>value)

U=M-1;

elseif(data[M]<value)

L=M+1;

else

returntrue;

}

returnfalse;

}

template<classtype>boolrecursive_binary_search(vector<type>data,intbegin,intend,typekey)

{

if(begin>=end)

returnfalse;

else

{

intmid=begin+(end-begin)/2;

if(data[mid]>key)

recursive_binary_search(data,begin,mid-1,key);

elseif(data[mid]<key)

recursive_binary_search(data,mid+1,end,key);

else

returntrue;

}

}

intmain()

{

/*auto_ptrdoesnotsupportforarrays,C11support*/

//auto_ptr<double>auto_ptr_data(newdouble);

//*auto_ptr_data=100;

//cout<<*auto_ptr_data<<endl;

vector<double>data;

for(unsignedinti=0;i<20;i++)

{

data.push_back(random<double>(1,10));

}

data.push_back(77.77);

vector<double>copy_data(data.size());

copy(data.begin(),data.end(),copy_data.begin());

for(unsignedinti=0;i<10;i++)

{

cout<<data[i]<<"=="<<copy_data[i]<<endl;

}

sort(data.begin(),data.end());

for(unsignedinti=0;i<data.size();i++)

if(binary_search(data.begin(),data.end(),copy_data[i]))

{

cout<<"founditem:"<<copy_data[i]<<endl;

}

/*-----testnon-recursiveversion-----*/

if(my_binary_search<double>(data,0,data.size(),898))

{

cout<<"finditem:"<<898<<endl;

}

else

cout<<"notfounditem:"<<898<<endl;

/*----testrecursivebinarysearch-----*/

vector<double>A(10,random(1,10));//初始化向量A，每一个元素都为1

for(inti=0;i<10;i++)

cout<<A[i]<<endl;

if(recursive_binary_search<double>(A,1,5,1))

cout<<"found!"<<endl;

return0;

}

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