#include <iostream>
#include <algorithm>
//Sorted Range上的查找算法
int main()
{
/************************************************************************/
//binary_search
/************************************************************************/
//binary_search:二分查找，在已排序的[first,last)中寻找元素value，如果存在返回true，否则返回false
/*
template<class ForwardIterator, class Type>
bool binary_search(
ForwardIterator _First,
ForwardIterator _Last,
const Type& _Val
);
template<class ForwardIterator, class Type, class BinaryPredicate>
bool binary_search(
ForwardIterator _First,
ForwardIterator _Last,
const Type& _Val,
BinaryPredicate _Comp
);
*/
int a[] = { 1, 2, 3, 3, 5, 8 };
int n = sizeof a / sizeof a[0];
/*运行结果
Element 0:not present
Element 1:present
Element 2:present
Element 3:present
Element 4:not present
Element 5:present
Element 6:not present
Element 7:not present
Element 8:present
Element 9:not present
*/
for (auto i = 0; i < 10; ++i)
{
std::cout << "Element " << i << ":" <<
(std::binary_search(std::begin(a), std::end(a), i) ? "present" : "not present")
<< std::endl;
}
std::cout << "===================================" << std::endl;
/************************************************************************/
//lower_bound
/************************************************************************/
/*lower_bound:试图在已排序的[first,last)中寻找元素value
如果存在value，则函数返回找到的第一个value元素的位置
如果不存在value，则返回应该出现的位置，即第一个不小于value元素的位置，或者说第一个可安插value的位置
*/
/*
template<class ForwardIterator, class Type>
ForwardIterator lower_bound(
ForwardIterator _First,
ForwardIterator _Last,
const Type& _Val
);
template<class ForwardIterator, class Type, class BinaryPredicate>
ForwardIterator lower_bound(
ForwardIterator _First,
ForwardIterator _Last,
const Type& _Val,
BinaryPredicate _Comp
);
*/
/*运行结果
Searching for 0. Result: index = 0, a[0] == 1
Searching for 1. Result: index = 0, a[0] == 1
Searching for 2. Result: index = 1, a[1] == 2
Searching for 3. Result: index = 2, a[2] == 3
Searching for 4. Result: index = 4, a[4] == 5
Searching for 5. Result: index = 4, a[4] == 5
Searching for 6. Result: index = 5, a[5] == 8
Searching for 7. Result: index = 5, a[5] == 8
Searching for 8. Result: index = 5, a[5] == 8
Searching for 9. Result: index = 6, which is off-the-end.
*/
for (auto i = 0; i < 10; ++i)
{
int *p = std::lower_bound(std::begin(a), std::end(a), i);
std::cout << "Searching for " << i << ". ";
std::cout << "Result: index = " << p - a << ", ";
if (p != std::end(a))
std::cout << "a[" << p - a << "] == " << *p << std::endl;
else
std::cout << "which is off-the-end." << std::endl;
}
std::cout << "=======================================" << std::endl;
/************************************************************************/
//upper_bound
/************************************************************************/
/*upper_bound:试图在已排序的[first,last)中寻找元素value
函数返回可被安插的最后一个合适的位置，所以value若存在，则返回的iterator将指向value的下一个位置
*/
/*
template<class ForwardIterator, class Type>
ForwardIterator upper_bound(
ForwardIterator _First,
ForwardIterator _Last,
const Type& _Val
);
template<class ForwardIterator, class Type, class Predicate>
ForwardIterator upper_bound(
ForwardIterator _First,
ForwardIterator _Last,
const Type& _Val,
Predicate _Comp
);
*/
int *p = std::upper_bound(std::begin(a), std::end(a), 3);
std::cout << "a[" << p - a << "] = " << *p << std::endl;//a[4] = 5
/*运行结果
Searching for 0. Result: index = 0, a[0] == 1
Searching for 1. Result: index = 1, a[1] == 2
Searching for 2. Result: index = 2, a[2] == 3
Searching for 3. Result: index = 4, a[4] == 5
Searching for 4. Result: index = 4, a[4] == 5
Searching for 5. Result: index = 5, a[5] == 8
Searching for 6. Result: index = 5, a[5] == 8
Searching for 7. Result: index = 5, a[5] == 8
Searching for 8. Result: index = 6, which is off-the-end.
Searching for 9. Result: index = 6, which is off-the-end.
*/
for (auto i = 0; i < 10; ++i)
{
int *p = std::upper_bound(std::begin(a), std::end(a), i);
std::cout << "Searching for " << i << ". ";
std::cout << "Result: index = " << p - a << ", ";
if (p != std::end(a))
std::cout << "a[" << p - a << "] == " << *p << std::endl;
else
std::cout << "which is off-the-end." << std::endl;
}
std::cout << "===================================" << std::endl;
/************************************************************************/
//equal_range
/************************************************************************/
/*equal_range:lower_bound与upper_bound的结合，
函数返回一对iterator i和j，i表示可安插的第一个位置，j表示可安插的最后一个位置,
*/
/*
template<class ForwardIterator, class Type>
pair<ForwardIterator, ForwardIterator> equal_range(
ForwardIterator _First,
ForwardIterator _Last,
const Type& _Val
);
template<class ForwardIterator, class Type, class Predicate>
pair<ForwardIterator, ForwardIterator> equal_range(
ForwardIterator _First,
ForwardIterator _Last,
const Type& _Val,
Predicate _Comp
);
*/
/*运行结果
Searching for 2
First position where 2 could be inserted: 1
Last position where 2 could be inserted: 2
*result.first = 2
*result.second = 3
Searching for 3
First position where 3 could be inserted: 2
Last position where 3 could be inserted: 4
*result.first = 3
*result.second = 5
Searching for 4
First position where 4 could be inserted: 4
Last position where 4 could be inserted: 4
*result.first = 5
*result.second = 5
Searching for 5
First position where 5 could be inserted: 4
Last position where 5 could be inserted: 5
*result.first = 5
*result.second = 8
*/
for (auto i = 2; i <= 5; ++i)
{
std::pair<int*, int*> result = std::equal_range(std::begin(a), std::end(a), i);
std::cout << std::endl;
std::cout << "Searching for " << i << std::endl;
std::cout << "First position where " << i << " could be inserted: " << result.first - a << std::endl;
std::cout << "Last position where " << i << " could be inserted: " << result.second - a << std::endl;
if (result.first < std::end(a))
std::cout << "*result.first = " << *result.first << std::endl;
if (result.second < std::end(a))
std::cout << "*result.second = " << *result.second << std::endl;
}
return 0;
}
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