std::adjacent_difference

 

C++

Language

Standard library headers

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Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Algorithm library

Functions
Non-modifying sequence operations
all_ofany_ofnone_of (C++11)(C++11)(C++11) for_each countcount_if mismatch equal	findfind_iffind_if_not (C++11) find_end find_first_of adjacent_find search search_n
Modifying sequence operations
copycopy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n removeremove_if remove_copyremove_copy_if	replacereplace_if replace_copyreplace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffleshuffle (until C++17)(C++11) unique unique_copy
Partitioning operations
is_partitioned (C++11) partition partition_copy (C++11)	stable_partition partition_point (C++11)
Sorting operations (on sorted ranges)
is_sorted (C++11) is_sorted_until (C++11) sort	partial_sort partial_sort_copy stable_sort nth_element
Binary search operations (on sorted ranges)
lower_bound upper_bound	binary_search equal_range
Set operations (on sorted ranges)
merge inplace_merge includes	set_difference set_intersection set_symmetric_difference set_union
Heap operations
is_heap (C++11) is_heap_until (C++11) make_heap	push_heap pop_heap sort_heap
Minimum/maximum operations
max max_element min min_element minmax (C++11) minmax_element (C++11)	lexicographical_compare is_permutation (C++11) next_permutation prev_permutation
Numeric operations
iota (C++11) accumulate inner_product	adjacent_difference partial_sum
C library
qsort	bsearch

 

Defined in header <numeric>
template< class InputIt, class OutputIt > OutputIt adjacent_difference( InputIt first, InputIt last,                               OutputIt d_first );	(1)
template< class InputIt, class OutputIt, class BinaryOperation > OutputIt adjacent_difference( InputIt first, InputIt last,                               OutputIt d_first, BinaryOperation op );	(2)

Computes the differences between the second and the first of each adjacent pair of elements of the range [first, last) and writes them to the range beginning at d_first + 1. Unmodified copy of first is written to d_first. The first version uses operator- to calculate the differences, the second version uses the given binary function op.

Equivalent operation:

*(d_first)   = *first;
*(d_first+1) = *(first+1) - *(first);
*(d_first+2) = *(first+2) - *(first+1);
*(d_first+3) = *(first+3) - *(first+2);
...

op must not have side effects.	(until C++11)
op must not invalidate any iterators, including the end iterators, or modify any elements of the ranges involved.	(since C++11)

Parameters

first, last	-	the range of elements
d_first	-	the beginning of the destination range
op	-	binary operation function object that will be applied. The signature of the function should be equivalent to the following:  Ret fun(const Type1 &a, const Type2 &b); The signature does not need to have const &. The types Type1 and Type2 must be such that an object of type iterator_traits<InputIt>::value_type can be implicitly converted to both of them. The type Ret must be such that an object of type OutputIt can be dereferenced and assigned a value of type Ret. ​
Type requirements
- InputIt must meet the requirements of InputIterator.
- OutputIt must meet the requirements of OutputIterator.

Return value

It to the element past the last element written.

Notes

If first == last, this function has no effect and will merely return d_first.

Complexity

Exactly (last - first) - 1 applications of the binary operation

Possible implementation

First version
template<class InputIt, class OutputIt> OutputIt adjacent_difference(InputIt first, InputIt last, OutputIt d_first) { if (first == last) return d_first;   typedef typename std::iterator_traits<InputIt>::value_type value_t; value_t acc = *first; *d_first = acc; while (++first != last) { value_t val = *first; *++d_first = val - acc; acc = std::move(val); } return ++d_first; }
Second version
template<class InputIt, class OutputIt, class BinaryOperation> OutputIt adjacent_difference(InputIt first, InputIt last, OutputIt d_first, BinaryOperation op) { if (first == last) return d_first;   typedef typename std::iterator_traits<InputIt>::value_type value_t; value_t acc = *first; *d_first = acc; while (++first != last) { value_t val = *first; *++d_first = op(val, acc); acc = std::move(val); } return ++d_first; }

Example

The following code converts a sequence of even numbers to repetitions of the number 2 and converts a sequence of ones to a sequence of Fibonacci numbers.

Run this code

​#include <numeric>
#include <vector>
#include <iostream>
#include <functional>
 
int main()
{
    std::vector<int> v{2, 4, 6, 8, 10, 12, 14, 16, 18, 20};
    std::adjacent_difference(v.begin(), v.end(), v.begin());
 
    for (auto n : v) {
        std::cout << n << ' ';
    }
    std::cout << '\n';
 
    v = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
    std::adjacent_difference(v.begin(), v.end() - 1, v.begin() + 1, std::plus<int>());
 
    for (auto n : v) {
        std::cout << n << ' ';
    }
    std::cout << '\n';
}​

Output:

2 2 2 2 2 2 2 2 2 2
1 1 2 3 5 8 13 21 34 55

See also

partial_sum	computes the partial sum of a range of elements (function template)
accumulate	sums up a range of elements (function template)
std::experimental::parallel::ajacent_difference (parallelism TS)	parallelized version of std::ajacent_difference (function template)