C++ STL（2）：线性查找

#include <iostream>
#include <algorithm>
#include <vector>
#include <cstring>

//STL：线性查找
int main()
{
    int a[] = {4, 1, 6, 9, 7, 1, 0};
    size_t len = sizeof a / sizeof a[0];

    typedef std::vector<int> vctype_int;
    vctype_int vi(a, a + len);

    /************************************************************************/
    //find
    //find_if
    /************************************************************************/
    //find：寻找范围内某一特定值，返回满足条件的第一个元素的迭代器
    /*
        template<class InputIterator, class Type>
        InputIterator find(
            InputIterator _First, 
            InputIterator _Last, 
            const Type& _Val
        );
    */
    vctype_int::iterator it = std::find(vi.begin(),vi.end(), 2);
    //it = std::find(begin(a), end(a), 2);
    if(it == vi.end())
        std::cout << "not found" << std::endl;//not found
    else
        std::cout << "found" << std::endl;

    //find_if：寻找范围内满足条件的第一个元素的迭代器，一般为不等于某个值的条件
    //当然也可以使用find_if来查找某个特定的值
    //如上代码可以改成如下代码：
    it = find_if(vi.begin(), vi.end(), bind1st(std::equal_to<int>(),2));
    if(it == vi.end())
        std::cout << "not found" << std::endl;//not found
    else
        std::cout << "found" << std::endl;
   
   /*
		template<class InputIterator, class Predicate>
	        InputIterator find_if(
			InputIterator _First, 
			InputIterator _Last, 
			Predicate _Pred
		);
	*/

	/*
		template<class InputIterator, class Predicate>
		typename iterator_traits<InputIterator>::difference_type count_if(
			InputIterator _First, 
			InputIterator _Last,
			Predicate _Pred
		);
	*/
	int val = 8;
	it = std::find_if(vi.begin(), vi.end(), [val](const int& e){return e > val;});
	if(it == vi.end())
		std::cout << "no elements is greater than" << val << std::endl;
	else
	{
		int nums = std::count_if(vi.begin(), vi.end(), [val](const int& e){return e > val;});
		std::cout << "has " << nums << " elements greater than " << val << std::endl;
		//has 1 elements greater than 8
	}

	//绑定操作（比较）函数的第一个参数
	/*
		template<class Operation, class Type>
		binder1st <Operation> bind1st(
			const Operation& _Func, 
			const Type& _Left
		);
	*/
	find_if(vi.begin(), vi.end(), bind1st(std::less<int>(),8));
	if(it == vi.end())
		std::cout << "no elements is greater than" << val << std::endl;
	else
	{
		int nums = std::count_if(vi.begin(), vi.end(), bind1st(std::less<int>(),8));
		std::cout << "has " << nums << " elements greater than " << val << std::endl;
		//has 1 elements greater than 8
	}

	//绑定操作（比较）函数的第二个参数
	/*
		template<class Operation, class Type>
		binder2nd <Operation> bind2nd(
			const Operation& _Func, 
			const Type& _Right
		);
	*/
	find_if(vi.begin(), vi.end(), bind2nd(std::less<int>(),8));
	if(it == vi.end())
		std::cout << "no elements is greater than" << val << std::endl;
	else
	{
		int nums = std::count_if(vi.begin(), vi.end(), bind2nd(std::less<int>(),8));
		std::cout << "has " << nums << " elements less than " << val << std::endl;
		//has 6 elements less than 8
	}

	/************************************************************************/
	//adjacent_find
	/************************************************************************/
	//版本1：查找两个相等的相邻元素，operator==
	//版本2：查找两个相邻元素是否满足某种条件,如果满足条件，则返回第一个满足条件的，function compare
	/*
		template<class ForwardIterator>
		ForwardIterator adjacent_find(
			ForwardIterator _First, 
			ForwardIterator _Last
		);
	*/
	/*
		template<class ForwardIterator , class BinaryPredicate>
		ForwardIterator adjacent_find(
			ForwardIterator _First, 
			ForwardIterator _Last, 
			BinaryPredicate _Comp
		);
	*/

	//测试版本1：
	int b[] = {1, 2, 6, 4, 4, 6, 7};
	len = sizeof b / sizeof b[0];
	int *p = std::adjacent_find(std::begin(b), std::end(b));
	if(p != b + len)
		std::cout << "Duplicate element: " << *p << std::endl;//Duplicate element: 4

	vi.clear();
	vi.assign(b, b + len);
	it = std::adjacent_find(vi.begin(), vi.end());
	if(it != vi.end())
		std::cout << "Duplicate element: " << *it << std::endl;//Duplicate element: 4


	//测试版本2：
	p = std::adjacent_find(std::begin(b), std::end(b), std::greater<int>());
	if(p == b + len)//未找到greater条件的元素，即升序
		std::cout << "Elements are sorted in ascending  order! " << std::endl;
	else
	{
		//Element 2 is out of order:6 > 4.即查找到greater条件的元素对
		std::cout << "Element " << p - b << " is out of order:" << *p << " > " << *(p + 1) << "." << std::endl;
	}

	/************************************************************************/
	//find_first_of
	/************************************************************************/
	//find_first_of：在范围[first1,last1)内查找任何出现与[first2,last2)内的元素，
	//类似strpbrk
	/*
		template<class ForwardIterator1, class ForwardIterator2>
		ForwardIterator1 find_first_of(
			ForwardIterator1 _First1, 
			ForwardIterator1 _Last1,
			ForwardIterator2 _First2, 
			ForwardIterator2 _Last2
		);
	*/
	/*
		template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
		ForwardIterator1 find_first_of(
			ForwardIterator1 _First1, 
			ForwardIterator1 _Last1,
			ForwardIterator2 _First2, 
			ForwardIterator2 _Last2,
			BinaryPredicate _Comp
		);
	*/

	const char *WS = " \t\n";
	const int n_WS = strlen(WS);

	char *s1 = "There sentence contains five words.";
	char *s2 = "OneWord";
	char *end1 = std::find_first_of(s1, s1 + strlen(s1), WS, WS + n_WS);
	char *end2 = std::find_first_of(s2, s2 + strlen(s2), WS, WS + n_WS);

	//first word of s1 : 5.
	std::cout << "first word of s1 : " << end1 - s1 << "." << std::endl;
	//first word of s1 : 7.
	std::cout << "first word of s1 : " << end2 - s2 << "." << std::endl;
	return 0;
}

运行结果：
not found
not found
has 1 elements greater than 8
has 1 elements greater than 8
has 6 elements less than 8

Duplicate element: 4
Duplicate element: 4

Element 2 is out of order:6 > 4.

first word of s1 : 5. 
first word of s1 : 7. 

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