Write the algorithm step by step (in the prim algorithm)

 

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C) write the minimal spanning tree, involving the process of creating, selecting, and adding

 

 

MINI_GENERATE_TREE * get_mini_tree_from_graph (GRAPH * pGraph)

{

MINI_GENERATE_TREE * pMiniTree;

DIR_LINE pDirLine;

 

If (NULL = pGraph | NULL = pGraph-> head)

Return NULL;

 

PMiniTree = (MINI_GENERATE_TREE *) malloc (sizeof (MINI_GENERATE_TREE ));

Assert (NULL! = PMiniTree );

Memset (pMiniTree, 0, sizeof (MINI_GENERATE_TREE ));

 

PMiniTree-> node_num = 1;

PMiniTree-> pNode = (int *) malloc (sizeof (int) * pGraph-> count );

Memset (pMiniTree-> pNode, 0, sizeof (int) * pGraph-> count );

PMiniTree-> pNode [0] = pGraph-> head-> start;

 

While (1 ){

Memset (& pDirLine, 0, sizeof (DIR_LINE ));

Get_dir_line_from_graph (pGraph, pMiniTree, & pDirLine );

If (pDirLine. start = 0)

Break;

 

PMiniTree-> line_num ++;

Insert_line_pai_queue (& pMiniTree-> pLine, pDirLine. start, pDirLine. end, pDirLine. weight );

Insert_node_into_mini_tree (& pDirLine, pMiniTree );

}

 

Return pMiniTree;

}

MINI_GENERATE_TREE * get_mini_tree_from_graph (GRAPH * pGraph)

{

MINI_GENERATE_TREE * pMiniTree;

DIR_LINE pDirLine;

 

If (NULL = pGraph | NULL = pGraph-> head)

Return NULL;

 

PMiniTree = (MINI_GENERATE_TREE *) malloc (sizeof (MINI_GENERATE_TREE ));

Assert (NULL! = PMiniTree );

Memset (pMiniTree, 0, sizeof (MINI_GENERATE_TREE ));

 

PMiniTree-> node_num = 1;

PMiniTree-> pNode = (int *) malloc (sizeof (int) * pGraph-> count );

Memset (pMiniTree-> pNode, 0, sizeof (int) * pGraph-> count );

PMiniTree-> pNode [0] = pGraph-> head-> start;

 

While (1 ){

Memset (& pDirLine, 0, sizeof (DIR_LINE ));

Get_dir_line_from_graph (pGraph, pMiniTree, & pDirLine );

If (pDirLine. start = 0)

Break;

 

PMiniTree-> line_num ++;

Insert_line_pai_queue (& pMiniTree-> pLine, pDirLine. start, pDirLine. end, pDirLine. weight );

Insert_node_into_mini_tree (& pDirLine, pMiniTree );

}

 

Return pMiniTree;

}

D) construct a selection function and select the most appropriate edge

 

Void get_dir_line_from_graph (GRAPH * pGraph, MINI_GENERATE_TREE * pMiniTree, DIR_LINE * pDirLine)

{

DIR_LINE * pHead;

DIR_LINE * prev;

VECTEX * pVectex;

LINE * pLine;

Int index;

Int start;

 

PHead = NULL;

For (index = 0; index <pMiniTree-> node_num; index ++ ){

Start = pMiniTree-> pNode [index];

PVectex = find_vectex_in_graph (pGraph-> head, start );

PLine = pVectex-> neighbor;

 

While (pLine ){

Insert_line_pai_queue (& pHead, start, pLine-> end, pLine-> weight );

PLine = pLine-> next;

}

}

 

If (NULL = pHead)

Return;

 

Delete_unvalid_line_from_list (& pHead, pMiniTree );

If (NULL = pHead)

Return;

 

Sort_for_line_list (& pHead );

Memmove (pDirLine, pHead, sizeof (DIR_LINE ));

 

While (pHead ){

Prev = pHead;

PHead = pHead-> next;

Free (prev );

}

Return;

}

Void get_dir_line_from_graph (GRAPH * pGraph, MINI_GENERATE_TREE * pMiniTree, DIR_LINE * pDirLine)

{

DIR_LINE * pHead;

DIR_LINE * prev;

VECTEX * pVectex;

LINE * pLine;

Int index;

Int start;

 

PHead = NULL;

For (index = 0; index <pMiniTree-> node_num; index ++ ){

Start = pMiniTree-> pNode [index];

PVectex = find_vectex_in_graph (pGraph-> head, start );

PLine = pVectex-> neighbor;

 

While (pLine ){

Insert_line_pai_queue (& pHead, start, pLine-> end, pLine-> weight );

PLine = pLine-> next;

}

}

 

If (NULL = pHead)

Return;

 

Delete_unvalid_line_from_list (& pHead, pMiniTree );

If (NULL = pHead)

Return;

 

Sort_for_line_list (& pHead );

Memmove (pDirLine, pHead, sizeof (DIR_LINE ));

 

While (pHead ){

Prev = pHead;

PHead = pHead-> next;

Free (prev );

}

Return;

}

 

 

 

E) Add a node function to include vertices that are not yet the minimum spanning tree into the minimum spanning tree.

 

 

Void insert_node_into_mini_tree (DIR_LINE * pLine, MINI_GENERATE_TREE * pMiniTree)

{

Int index;

 

For (index = 0; index <pMiniTree-> node_num; index ++ ){

If (pLine-> start = pMiniTree-> pNode [index]) {

PMiniTree-> pNode [pMiniTree-> node_num ++] = pLine-> end;

Return;

}

}

 

PMiniTree-> pNode [pMiniTree-> node_num ++] = pLine-> start;

Return;

}

Void insert_node_into_mini_tree (DIR_LINE * pLine, MINI_GENERATE_TREE * pMiniTree)

{

Int index;

 

For (index = 0; index <pMiniTree-> node_num; index ++ ){

If (pLine-> start = pMiniTree-> pNode [index]) {

PMiniTree-> pNode [pMiniTree-> node_num ++] = pLine-> end;

Return;

}

}

 

PMiniTree-> pNode [pMiniTree-> node_num ++] = pLine-> start;

Return;

}

Note:

 

(1) d and e are subfunctions called in c. If you observe them, you will understand them.

 

(2) The Minimum Spanning Tree is written in the top-down order. Although the subfunctions in c are completed, two subfunctions in d are not located.

 

(3) functions delete_unvalid_line_from_list and sort_for_line_list in d will be further introduced in the next article.

 

(4) As long as the algorithm can be compiled according to the manual calculation process, it is basically not a problem, but some details should be noted with caution.

 

 

 

 

 

[To be continued]