std::bsearch ('bsearch' is an abbreviation of 'binary search') is an STL algorithm to search for a value in a sorted container.

Download the Qt Creator project 'CppBsearch' (zip)


#include <algorithm>

#include <iostream>

#include <vector>



//The function to compare two elements

int CompareInt(const void * const a, const void * const b)

{

  const int x = *static_cast<const int *>(a);

  const int y = *static_cast<const int *>(b);

  if (x < y) return -1;

  if (x > y) return  1;

  return 0;

}



//Create a sorted vector of squares

const std::vector<int> CreateVector()

{

  std::vector<int> v;

  for (int i=0; i!=10; ++i) v.push_back(i*i);

  return v;

}



int main ()

{

  //Create a sorted vector of squares

  const std::vector<int> v = CreateVector();

  for (int i=0; i!=10; ++i)

  {

    //Search for i in v

    const int * const p = static_cast<const int*>(

      std::bsearch(&i,&v[0],v.size(),sizeof(int),CompareInt));

    //Display if i is present

    std::cout << i << " is " << (p ? "" : "not") << " present\n";

  }

}

Screen output:


0 is  present

1 is  present

2 is not present

3 is not present

4 is  present

5 is not present

6 is not present

7 is not present

8 is not present

9 is  present

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(C++) std::bsearch