C++ Tutorial/STL Algorithms Binary search/lower bound

Lower bound of 6

<source lang="cpp">#include <iostream>

1. include <algorithm>
2. include <vector>

using namespace std; int main() {

  const int SIZE = 10;
  int a1[] = { 2, 2, 4, 4, 4, 6, 6, 6, 6, 8 };
  vector< int > v( a1, a1 + SIZE );
  vector< int >::iterator lower;
  lower = lower_bound( v.begin(), v.end(), 6 );
  cout << "\n\nLower bound of 6 is element " << ( lower - v.begin() ) << " of vector v";
  return 0;

}</source>

Return an iterator from std::lower_bound

<source lang="cpp">#include <iostream> using std::cout; using std::endl;

1. include <algorithm>
2. include <vector>
3. include <iterator>

int main() {

  int a1[ 10 ] = { 2, 2, 4, 4, 4, 6, 6, 6, 6, 8 };
  std::vector< int > v( a1, a1 + 10 );
  std::ostream_iterator< int > output( cout, " " );
  std::copy( v.begin(), v.end(), output );
  std::vector< int >::iterator lower;
  lower = std::lower_bound( v.begin(), v.end(), 6 );
  cout << ( lower - v.begin() );
  return 0;

}</source>

2 2 4 4 4 6 6 6 6 8 5

Use lower_bound to locate the first point at which 5 can be inserted in order

<source lang="cpp">#include <iostream>

1. include <algorithm>
2. include <vector>

using namespace std; int main() {

  const int SIZE = 10;
  int a1[] = { 2, 2, 4, 4, 4, 6, 6, 6, 6, 8 };
  vector< int > v( a1, a1 + SIZE );
  vector< int >::iterator lower;
  cout << "\n\nUse lower_bound to locate the first point\n" << "at which 5 can be inserted in order";
  lower = lower_bound( v.begin(), v.end(), 5 );
  cout << "\n   Lower bound of 5 is element " << ( lower - v.begin() ) << " of vector v";
  return 0;

}</source>