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Difference between revisions of "cpp/algorithm/lower bound"

From cppreference.com
< cpp‎ | algorithm
(Equivalent function: formatting)
(Equivalent function: rm duplication. do not span across several lines.)
Line 38: Line 38:
 
                             const T& value)
 
                             const T& value)
 
{
 
{
     ForwardIterator it;
+
     typedef typename std::iterator_traits<InputIterator>::value_type value_t;
    std::iterator_traits<ForwardIterator>::distance_type count, step;
+
     return std::lower_bound(first, last, value, std::less<value_t>());
     count = std::distance(first, last);
+
 
+
    while (count > 0) {
+
        it = first;
+
        step = count / 2;
+
        std::advance(it, step);
+
        if (*it < value) {
+
            first = ++it;
+
            count -= step + 1;
+
        } else count = step;
+
    }
+
    return first;
+
 
}
 
}
 
  | 2=
 
  | 2=

Revision as of 14:36, 24 August 2011

Template:cpp/algorithm/sidebar Template:ddcl list begin <tr class="t-dsc-header">

<td>
Defined in header <algorithm>
</td>

<td></td> <td></td> <tr class="t-dcl ">

<td >
template< class ForwardIterator, class T >

ForwardIterator lower_bound( ForwardIterator first, ForwardIterator last,

                             const T& value );
</td>

<td > (1) </td> <td class="t-dcl-nopad"> </td> </tr> <tr class="t-dcl ">

<td >
template< class ForwardIterator, class T, class Compare >

ForwardIterator lower_bound( ForwardIterator first, ForwardIterator last,

                             const T& value, Compare comp );
</td>

<td > (2) </td> <td class="t-dcl-nopad"> </td> </tr> Template:ddcl list end

Returns an iterator pointing to the first element in the range [first, last) that is not less than value. The first version uses Template:cpp to compare the elements, the second version uses the given comparison function comp.

Contents

Parameters

first, last - iterators defining the range to examine
value - value to compare the elements to
comp - comparison function object (i.e. an object that satisfies the requirements of Compare) which returns ​true if the first argument is less than the second.

The signature of the comparison function should be equivalent to the following:

 bool cmp(const Type1 &a, const Type2 &b);

The signature does not need to have const &, but the function object must not modify the objects passed to it.
The type Type1 must be such that an object of type T can be implicitly converted to Type1. The type Type2 must be such that an object of type ForwardIterator can be dereferenced and then implicitly converted to Type2. ​

Return value

iterator pointing to the first element that is not less than value, or last if no such element is found.

Complexity

logarithmic in the distance between first and last

Equivalent function

Template:eq fun cpp

Example

Template:example cpp

See also

Template:cpp/algorithm/dcl list equal rangeTemplate:cpp/algorithm/dcl list upper bound