STL algorithm算法find_if_not(20)

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最新推荐文章于 2025-03-24 20:58:38 发布

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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 which pred returns false. If no such element is found, the function returns last.

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:

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 iterators to the initial and final positions in a sequence. The range used is [first,last), which contains all the elements between first and last, including the element pointed by first but not the element pointed by last.
要匹配的范围。

pred

Unary function that accepts an element in the range as argument and returns a value convertible to bool. 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 which pred returns false.
If pred is true for all elements, the function returns last.

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

// 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;
}