c How to use the collection

Header files included:

#include

#include

Set functions: sets1, s2;

Insert an element 1

Insert an element 2

set::iterator site;Iterator, used in the same way as vector

setsi;

setvis

set intersection( ,inserter( si, si is the set after the intersection.

set_union(..And, the grammar is the same as above.

set_difference(..Poor, the grammar is the same as above.

Remove all elements from the set container.

Returns the number of VIS with a median value of s.

if( to determine whether s is in the set vis.

Return the location of s, if you can't find it, return end(), which is vis,(s)== Add s to the collection.

Remove s from the collection

Output: set::iterator ii;

for(ii=;ii!=;ii++)

cout<<(ii)<<' ';

It is recommended to use std::set--element that is not allowed to be duplicated, or std::multiset-element that is allowed to be duplicated. Both of these collections are very efficient.

*Usage examples:

std::setmyset;

int a,b,c,d;

a=1;a=2;

a=3;a=4;;;

erase(), find(), and size() are functions that delete, find, and find the number of elements.

You may ask, why not just use arrays? The biggest advantage of std::set arrays is that the elements in the set are sorted by key values.

If std::set encounters duplicate key values, only one value is saved; Whereas, std::multiset allows duplicate elements to exist side by side.

Write the C++ program as you want to write and round the print of all subsets of the set with n elements as follows (see Figure Wu Pengxiang).

Use recursive Ying Xun to get all the subsets of a set with n elements (C++ implementation)**Brief description of the topic: For example, there is a set, find all its subsetsAnalysis: In fact, this is a problem of permutations and combinations; The existence of each element is represented by 0,1, which is a permutation of 0,1, and put it in an array, which can be achieved recursively.