thrust

◆ unique_by_key_copy() [2/4]

template<typename InputIterator1 , typename InputIterator2 , typename OutputIterator1 , typename OutputIterator2 >
thrust::pair<OutputIterator1,OutputIterator2> thrust::unique_by_key_copy ( InputIterator1  keys_first,
InputIterator1  keys_last,
InputIterator2  values_first,
OutputIterator1  keys_result,
OutputIterator2  values_result 
)

unique_by_key_copy is a generalization of unique_copy to key-value pairs. For each group of consecutive keys in the range [keys_first, keys_last) that are equal, unique_by_key_copy copies the first element of the group to a range beginning with keys_result and the corresponding values from the range [values_first, values_first + (keys_last - keys_first)) are copied to a range beginning with values_result.

This version of unique_by_key_copy uses operator== to test for equality and project1st to reduce values with equal keys.

Parameters
keys_firstThe beginning of the input key range.
keys_lastThe end of the input key range.
values_firstThe beginning of the input value range.
keys_resultThe beginning of the output key range.
values_resultThe beginning of the output value range.
Returns
A pair of iterators at end of the ranges [keys_result, keys_result_last) and [values_result, values_result_last).
Template Parameters
InputIterator1is a model of Input Iterator,
InputIterator2is a model of Input Iterator,
OutputIterator1is a model of Output Iterator and and InputIterator1's value_type is convertible to OutputIterator1's value_type.
OutputIterator2is a model of Output Iterator and and InputIterator2's value_type is convertible to OutputIterator2's value_type.
Precondition
The input ranges shall not overlap either output range.

The following code snippet demonstrates how to use unique_by_key_copy to compact a sequence of key/value pairs and with equal keys.

#include <thrust/unique.h>
...
const int N = 7;
int A[N] = {1, 3, 3, 3, 2, 2, 1}; // input keys
int B[N] = {9, 8, 7, 6, 5, 4, 3}; // input values
int C[N]; // output keys
int D[N]; // output values
new_end = thrust::unique_by_key_copy(A, A + N, B, C, D);
// The first four keys in C are now {1, 3, 2, 1} and new_end.first - C is 4.
// The first four values in D are now {9, 8, 5, 3} and new_end.second - D is 4.
See also
unique_copy
unique_by_key
reduce_by_key