STL algorithm算法find_if_not(20)

原文地址：http://www.cplusplus.com/reference/algorithm/find_if_not/

function template

<algorithm>

std::find_if_not

template <class InputIterator, class UnaryPredicate>
   InputIterator find_if_not (InputIterator first, InputIterator last, UnaryPredicate pred);

Find element in range (negative condition)

Returns an iterator to the first element in the range[first,last)for whichpredreturnsfalse. If no such element is found, the function returnslast.

跟find_if刚好相反，返回第一个不符合要求的元素的迭代器。如果没有匹配的，则返回last.

例子：

#include <iostream>
#include <vector>
#include <array>
#include <algorithm>
using namespace std;
void findifnot()
{
    vector<int> v1{100,200,300,400,155,300};
    array<int,3> ai{4,8,3};

    cout<<"v1=";
    for(int &i:v1)
        cout<<i<<"  ";
    cout<<endl;



    cout<<endl<<"auto it=find_if_not(v1.begin(),v1.end(),[](int i){return i%100==0;);"<<endl;
    auto it=find_if_not(v1.begin(),v1.end(),[](int i){return i%100==0;});
    cout<<"*(it-1)="<<*(it-1)<<endl;
    cout<<"*it="<<*it<<endl;
    cout<<"*(it+1)="<<*(it+1)<<endl;

    cout<<"ai=";
    for(int &i:ai)
        cout<<i<<"  ";
    cout<<endl<<"auto it2=find_first_of_not(ai.begin(),ai.end(),[](int i){return i%2==0;);"<<endl;
    auto it2=find_if_not(ai.begin(),ai.end(),[](int i){return i%2==0;});
    cout<<"*(it2-1)="<<*(it2-1)<<endl;
    cout<<"*it2="<<*it2<<endl;
    cout<<"*(it2+1)="<<*(it2+1)<<endl;

}

运行截图:

The behavior of this function template is equivalent to:

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template<class InputIterator, class UnaryPredicate> InputIterator find_if_not (InputIterator first, InputIterator last, UnaryPredicate pred) { while (first!=last) { if (!pred(*first)) return first; ++first; } return last; }

Parameters

first, last

Input iteratorsto the initial and final positions in a sequence. The range used is[first,last), which contains all the elements betweenfirstandlast, including the element pointed byfirstbut not the element pointed bylast.
要匹配的范围。

pred

Unary function that accepts an element in the range as argument and returns a value convertible tobool. The value returned indicates whether the element is considered a match in the context of this function.
The function shall not modify its argument.
This can either be a function pointer or a function object.
一个接受一个参数并返回一个bool值的一元函数。

Return value

An iterator to the first element in the range for whichpredreturnsfalse.
Ifpredistruefor all elements, the function returnslast.

返回第一个不符合要求的元素的迭代器。如果没有匹配的，则返回last.

Example

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// find_if_not example #include <iostream> // std::cout #include <algorithm> // std::find_if_not #include <array> // std::array int main () { std::array<int,5> foo = {1,2,3,4,5}; std::array<int,5>::iterator it = std::find_if_not (foo.begin(), foo.end(), [](int i){return i%2;} ); std::cout << "The first even value is " << *it << '\n'; return 0; }

Edit & Run

Output:

The first even value is 2

Complexity

Up to linear in thedistancebetweenfirstandlast: Callspredfor each element until a mismatch is found.

Data races

Some (or all) of the objects in the range[first,last)are accessed (once at most).

Exceptions

Throws if eitherpredor an operation on an iterator throws.
Note that invalid parameters causeundefined behavior.

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转载请注明出处：http://blog.csdn.net/qq844352155

author:天下无双

Email:[e-mail]

2014-9-13

于GDUT

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