| // Copyright (C) 2011 Davis E. King ([email protected]) | |
| // License: Boost Software License See LICENSE.txt for the full license. | |
| namespace dlib | |
| { | |
| // ---------------------------------------------------------------------------------------- | |
| class disjoint_subsets | |
| { | |
| /*! | |
| INITIAL VALUE | |
| - size() == 0 | |
| WHAT THIS OBJECT REPRESENTS | |
| This object represents a set of integers which is partitioned into | |
| a number of disjoint subsets. It supports the two fundamental operations | |
| of finding which subset a particular integer belongs to as well as | |
| merging subsets. | |
| !*/ | |
| public: | |
| void clear ( | |
| ) noexcept; | |
| /*! | |
| ensures | |
| - #size() == 0 | |
| - returns this object to its initial value | |
| !*/ | |
| void set_size ( | |
| unsigned long new_size | |
| ); | |
| /*! | |
| ensures | |
| - #size() == new_size | |
| - for all valid i: | |
| - #find_set(i) == i | |
| (i.e. this object contains new_size subsets, each containing exactly one element) | |
| !*/ | |
| size_t size ( | |
| ) const noexcept; | |
| /*! | |
| ensures | |
| - returns the total number of integer elements represented | |
| by this object. | |
| !*/ | |
| unsigned long find_set ( | |
| unsigned long item | |
| ) const; | |
| /*! | |
| requires | |
| - item < size() | |
| ensures | |
| - Each disjoint subset can be represented by any of its elements (since | |
| the sets are all disjoint). In particular, for each subset we define | |
| a special "representative element" which is used to represent it. | |
| Therefore, this function returns the representative element for the | |
| set which contains item. | |
| - find_set(find_set(item)) == find_set(item) | |
| - Note that if A and B are both elements of the same subset then we always | |
| have find_set(A) == find_set(B). | |
| !*/ | |
| unsigned long merge_sets ( | |
| unsigned long a, | |
| unsigned long b | |
| ); | |
| /*! | |
| requires | |
| - a != b | |
| - a < size() | |
| - b < size() | |
| - find_set(a) == a | |
| (i.e. a is the representative element of some set) | |
| - find_set(b) == b | |
| (i.e. b is the representative element of some set) | |
| ensures | |
| - #find_set(a) == #find_set(b) | |
| (i.e. merges the set's containing a and b) | |
| - returns #find_set(a) | |
| !*/ | |
| }; | |
| // ---------------------------------------------------------------------------------------- | |
| } | |