Apache C++ Standard Library User's Guide

## 13.1 Overview

In this chapter and in Chapter 14 we examine and illustrate each of the generic algorithms provided by the C++ Standard Library. The names and a short description of each of the algorithms in this chapter are given in Table 19. We have divided the algorithms into several categories, based on how they are typically used. This division differs from the categories used in the C++ Standard Library definition, which is based upon whether or not the algorithms modify their arguments.

#### Table 19: Generic algorithms of the C++ Standard Library

 Algorithm Purpose Algorithms initializing a sequence copy() Copies a sequence into another sequence copy_backward() Copies a sequence into another sequence fill() Fills a sequence with an initial value fill_n() Fills n positions with an initial value generate() Initializes a sequence using a generator generate_n() Initializes n positions using a generator swap() Exchanges values swap_ranges() Swaps values from two parallel sequences Searching algorithms adjacent_find() Finds consecutive duplicate elements find() Finds an element matching the argument find_end() Finds the last occurrence of a sub-sequence in a sequence find_first_of() Finds the first occurrence of one member of a sequence in another sequence find_if() Finds an element satisfying a condition max_element() Finds the maximum value in a sequence min_element() Finds the minimum value in a sequence mismatch() Finds first mismatch in parallel sequences search() Matches a sub-sequence within a sequence Algorithms for in-place transformations inplace_merge() Merges two adjacent sequences into one next_permutation() Generates permutations in sequence partition() Partitions elements into two groups permutation() Generates successive permutations of a sequence based on an ordering function prev_permutation() Generates permutations in reverse sequence random_shuffle() Randomly rearranges elements in a sequence replace() Replaces specific values with new value replace_if() Replaces elements matching predicate reverse() Reverses the elements in a sequence rotate() Rotates elements in a sequence around a point stable_partition() Partitions preserving original ordering Removal algorithms remove() Removes elements that match condition unique() Removes all but first of duplicate values in sequences Scalar-producing algorithms accumulate() Reduces sequence to a scalar value count() Counts number of elements matching value count_if() Counts elements matching predicate equal() Checks two sequences for equality inner_product() Gives inner product of two parallel sequences lexicographical_compare() Compares two sequences Sequence-generating algorithms adjacent_difference() Generates sequence of adjacent differences partial_sum() Generates sequence of partial sums transform() Transforms each element Miscellaneous operations for_each() Applies a function to each element of a collection

In this chapter, we illustrate the use of each algorithm with a series of short examples. Many of the algorithms are also used in the sample programs provided in the chapters on the various container classes. These cross references have been noted where appropriate.

All the short example programs described in this section are contained in a number of files, named alg1.cpp through alg6.cpp. In the files, the example programs are augmented with output statements describing the test programs and illustrating the results of executing the algorithms. So as not to confuse the reader with unnecessary detail, we have generally omitted these output statements from the descriptions here. If you wish to see the test programs complete with output statements, you can compile and execute the test files. The expected output from these programs is also included in the distribution.

### 13.1.1 Include Files

To use any of the generic algorithms, you must first include the appropriate header file. The majority of the functions are defined in the header file algorithm. The functions std::accumulate(), std::inner_product(), std::partial_sum(), and std::adjacent_difference() are defined in the header file numeric.

```#include <algorithm>
#include <numeric>
```