thrust

◆ set_union_by_key() [2/4]

template<typename InputIterator1 , typename InputIterator2 , typename InputIterator3 , typename InputIterator4 , typename OutputIterator1 , typename OutputIterator2 >
thrust::pair<OutputIterator1,OutputIterator2> thrust::set_union_by_key ( InputIterator1  keys_first1,
InputIterator1  keys_last1,
InputIterator2  keys_first2,
InputIterator2  keys_last2,
InputIterator3  values_first1,
InputIterator4  values_first2,
OutputIterator1  keys_result,
OutputIterator2  values_result 
)

set_union_by_key performs a key-value union operation from set theory. set_union_by_key constructs a sorted range that is the union of the sorted ranges [keys_first1, keys_last1) and [keys_first2, keys_last2). Associated with each element from the input and output key ranges is a value element. The associated input value ranges need not be sorted.

In the simplest case, set_union_by_key performs the "union" operation from set theory: the output range contains a copy of every element that is contained in [keys_first1, keys_last1), [keys_first2, keys_last1), or both. The general case is more complicated, because the input ranges may contain duplicate elements. The generalization is that if [keys_first1, keys_last1) contains m elements that are equivalent to each other and if [keys_first2, keys_last2) contains n elements that are equivalent to them, then all m elements from the first range shall be copied to the output range, in order, and then max(n - m, 0) elements from the second range shall be copied to the output, in order.

Each time a key element is copied from [keys_first1, keys_last1) or [keys_first2, keys_last2) is copied to the keys output range, the corresponding value element is copied from the corresponding values input range (beginning at values_first1 or values_first2) to the values output range.

This version of set_union_by_key compares key elements using operator<.

Parameters
keys_first1The beginning of the first input range of keys.
keys_last1The end of the first input range of keys.
keys_first2The beginning of the second input range of keys.
keys_last2The end of the second input range of keys.
values_first1The beginning of the first input range of values.
values_first2The beginning of the first input range of values.
keys_resultThe beginning of the output range of keys.
values_resultThe beginning of the output range of values.
Returns
A pair p such that p.first is the end of the output range of keys, and such that p.second is the end of the output range of values.
Template Parameters
InputIterator1is a model of Input Iterator, InputIterator1 and InputIterator2 have the same value_type, InputIterator1's value_type is a model of LessThan Comparable, the ordering on InputIterator1's value_type is a strict weak ordering, as defined in the LessThan Comparable requirements, and InputIterator1's value_type is convertable to a type in OutputIterator's set of value_types.
InputIterator2is a model of Input Iterator, InputIterator2 and InputIterator1 have the same value_type, InputIterator2's value_type is a model of LessThan Comparable, the ordering on InputIterator2's value_type is a strict weak ordering, as defined in the LessThan Comparable requirements, and InputIterator2's value_type is convertable to a type in OutputIterator's set of value_types.
InputIterator3is a model of Input Iterator, and InputIterator3's value_type is convertible to a type in OutputIterator2's set of value_types.
InputIterator4is a model of Input Iterator, and InputIterator4's value_type is convertible to a type in OutputIterator2's set of value_types.
OutputIterator1is a model of Output Iterator.
OutputIterator2is a model of Output Iterator.
Precondition
The ranges [keys_first1, keys_last1) and [keys_first2, keys_last2) shall be sorted with respect to operator<.
The resulting ranges shall not overlap with any input range.

The following code snippet demonstrates how to use set_symmetric_difference_by_key to compute the symmetric difference of two sets of integers sorted in ascending order with their values.

...
int A_keys[6] = {0, 2, 4, 6, 8, 10, 12};
int A_vals[6] = {0, 0, 0, 0, 0, 0, 0};
int B_keys[5] = {1, 3, 5, 7, 9};
int B_vals[5] = {1, 1, 1, 1, 1};
int keys_result[11];
int vals_result[11];
thrust::pair<int*,int*> end = thrust::set_symmetric_difference_by_key(A_keys, A_keys + 6, B_keys, B_keys + 5, A_vals, B_vals, keys_result, vals_result);
// keys_result is now {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12}
// vals_result is now {0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0}
See also
set_symmetric_difference_by_key
set_intersection_by_key
set_difference_by_key
sort_by_key
is_sorted