STL algorithm算法find_if(19)

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

function template

std::find_if

template 
   InputIterator find_if (InputIterator first, InputIterator last, UnaryPredicate pred);

Find element in range

Returns an iterator to the first element in the range [first,last) for which pred returns true. If no such element is found, the function returns last.
返回范围内第一个符合要求的元素的迭代器，如果没有，则返回last.

#include 
#include 
#include 
#include 
using namespace std;
void findif()
{
    vector v1{1,2,3,4,5,6,3,4,9,8};
    array ai{77,88};

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


 The behavior of this function template is equivalent to:
 
  
 
   
 
    
 
     
 
      
 
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template
  InputIterator find_if (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.
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. 
   
 
  
 
  一元函数。（接受一个参数的一元函数，返回一个bool值）
 
  
 Return value
 
  An iterator to the first element in the range for which pred does not return false.
 If pred is false for all elements, the function returns last.
 
   
  
 
  
返回范围内第一个符合要求的元素的迭代器，如果没有，则返回last.
 
  
 
   
 
  
 
   
  
 
  
 
  
 
  
 Example
 
  
 
   
 
    
 
     
 
      
 
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// find_if example
#include      // std::cout
#include     // std::find_if
#include        // std::vector

bool IsOdd (int i) {
  return ((i%2)==1);
}

int main () {
  std::vector myvector;

  myvector.push_back(10);
  myvector.push_back(25);
  myvector.push_back(40);
  myvector.push_back(55);

  std::vector::iterator it = std::find_if (myvector.begin(), myvector.end(), IsOdd);
  std::cout << "The first odd value is " << *it << '\n';

  return 0;
}
 
 
      
 
       
 
        
 
         
 
          Edit & Run 
         
 
        
 
       
 
 
     
 
    
 
   
 
  
 
  

 Output:
 
  
 
   
 
    
 
     
 
      
 
The first odd value is 25
 
 
     
 
    
 
   
 
  
 
  
 
  
 Complexity
 
  Up to linear in the distance between first and last: Calls pred for each element until a match is found.
 
  
 
  
 Data races
 
  Some (or all) of the objects in the range [first,last) are accessed (once at most).
 
  
 
  
 Exceptions
 
  Throws if either pred or an operation on an iterator throws.
 Note that invalid parameters cause undefined behavior. 
  
 
  
 
   
  
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 转载请注明出处：http://blog.csdn.net/qq844352155
 
  
 author:天下无双
 
  
 Email:[email protected]
 
  
 
 
  
 2014-9-12
 
  
 于GDUT
 
  
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