binary_search

  #include <algorithm>
  bool binary_search( iterator start, iterator end, const TYPE& val );
  bool binary_search( iterator start, iterator end, const TYPE& val, Comp f );

The binary_search() function searches from start to end for val. The elements between start and end that are searched should be in ascending order as defined by the < operator. Note that a binary search will not work unless the elements being searched are in order.

If val is found, binary_search() returns true, otherwise false.

If the function f is specified, then it is used to compare elements.

For example, the following code uses binary_search() to determine if the integers 0-9 are in an array of integers:

 int nums[] = { -242, -1, 0, 5, 8, 9, 11 };
 int start = 0;
 int end = 7;           

 for( int i = 0; i < 10; i++ ) {
   if( binary_search( nums+start, nums+end, i ) ) {
     cout << "nums[] contains " << i << endl;
   } else {
     cout << "nums[] DOES NOT contain " << i << endl;
   }
 }              

When run, this code displays the following output:

 nums[] contains 0
 nums[] DOES NOT contain 1
 nums[] DOES NOT contain 2
 nums[] DOES NOT contain 3
 nums[] DOES NOT contain 4
 nums[] contains 5
 nums[] DOES NOT contain 6
 nums[] DOES NOT contain 7
 nums[] contains 8
 nums[] contains 9