thrust

◆ equal_range() [2/4]

template<class ForwardIterator , class LessThanComparable >
thrust::pair<ForwardIterator, ForwardIterator> thrust::equal_range ( ForwardIterator  first,
ForwardIterator  last,
const LessThanComparable &  value 
)

equal_range is a version of binary search: it attempts to find the element value in an ordered range [first, last). The value returned by equal_range is essentially a combination of the values returned by lower_bound and upper_bound: it returns a pair of iterators i and j such that i is the first position where value could be inserted without violating the ordering and j is the last position where value could be inserted without violating the ordering. It follows that every element in the range [i, j) is equivalent to value, and that [i, j) is the largest subrange of [first, last) that has this property.

This version of equal_range returns a pair of iterators [i, j), where i is the furthermost iterator in [first, last) such that, for every iterator k in [first, i), *k < value. j is the furthermost iterator in [first, last) such that, for every iterator k in [first, j), value < *k is false. For every iterator k in [i, j), neither value < *k nor *k < value is true.

Parameters
firstThe beginning of the ordered sequence.
lastThe end of the ordered sequence.
valueThe value to be searched.
Returns
A pair of iterators [i, j) that define the range of equivalent elements.
Template Parameters
ForwardIteratoris a model of Forward Iterator.
LessThanComparableis a model of LessThanComparable.

The following code snippet demonstrates how to use equal_range to search for values in a ordered range.

...
thrust::device_vector<int> input(5);
input[0] = 0;
input[1] = 2;
input[2] = 5;
input[3] = 7;
input[4] = 8;
thrust::equal_range(input.begin(), input.end(), 0); // returns [input.begin(), input.begin() + 1)
thrust::equal_range(input.begin(), input.end(), 1); // returns [input.begin() + 1, input.begin() + 1)
thrust::equal_range(input.begin(), input.end(), 2); // returns [input.begin() + 1, input.begin() + 2)
thrust::equal_range(input.begin(), input.end(), 3); // returns [input.begin() + 2, input.begin() + 2)
thrust::equal_range(input.begin(), input.end(), 8); // returns [input.begin() + 4, input.end)
thrust::equal_range(input.begin(), input.end(), 9); // returns [input.end(), input.end)
See also
http://www.sgi.com/tech/stl/equal_range.html
lower_bound
upper_bound
binary_search