binary_search

原型

默认

template <class ForwardIterator, class T>
  bool binary_search (ForwardIterator first, ForwardIterator last,
                      const T& val);

有比较函数

template <class ForwardIterator, class T, class Compare>
  bool binary_search (ForwardIterator first, ForwardIterator last,
                      const T& val, Compare comp);

样列

// binary_search example
#include <iostream>     // std::cout
#include <algorithm>    // std::binary_search, std::sort
#include <vector>       // std::vector

bool myfunction (int i,int j) { return (i<j); }

int main () {
  int myints[] = {1,2,3,4,5,4,3,2,1};
  std::vector<int> v(myints,myints+9);                         // 1 2 3 4 5 4 3 2 1

  // using default comparison:
  std::sort (v.begin(), v.end());

  std::cout << "looking for a 3... ";
  if (std::binary_search (v.begin(), v.end(), 3))
    std::cout << "found!\n"; else std::cout << "not found.\n";

  // using myfunction as comp:
  std::sort (v.begin(), v.end(), myfunction);

  std::cout << "looking for a 6... ";
  if (std::binary_search (v.begin(), v.end(), 6, myfunction))
    std::cout << "found!\n"; else std::cout << "not found.\n";

  return 0;
}

输出:

looking for a 3... found!
looking for a 6... not found.