Write an algorithm step by step (create a graph)

 

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We have discussed the basic structure of a graph. It can be matrix type, array type, or pointer type. Of course, for me, the structure I prefer is the linked list pointer type. Essentially, a graph consists of many nodes, each of which has many branches. To this end, we made a small change to the original structure:

 

 

Typedef struct _ LINE

{

Int end;

Int weight;

Struct _ LINE * next;

} LINE;

 

Typedef struct _ VECTEX

{

Int start;

Int number;

LINE * neighbor;

Struct _ VECTEX * next;

} VECTEX;

 

Typedef struct _ GRAPH

{

Int count;

VECTEX * head;

} GRAPH;

Typedef struct _ LINE

{

Int end;

Int weight;

Struct _ LINE * next;

} LINE;

 

Typedef struct _ VECTEX

{

Int start;

Int number;

LINE * neighbor;

Struct _ VECTEX * next;

} VECTEX;

 

Typedef struct _ GRAPH

{

Int count;

VECTEX * head;

} GRAPH; To create a GRAPH, you must first create a node and an edge. Start with creating a node,

 

 

VECTEX * create_new_vectex (int start)

{

VECTEX * pVextex = (VECTEX *) malloc (sizeof (VECTEX ));

Assert (NULL! = PVextex );

 

PVextex-> start = start;

PVextex-> number = 0;

PVextex-> neighbor = NULL ;;

PVextex-> next = NULL;

Return pVextex;

}

VECTEX * create_new_vectex (int start)

{

VECTEX * pVextex = (VECTEX *) malloc (sizeof (VECTEX ));

Assert (NULL! = PVextex );

 

PVextex-> start = start;

PVextex-> number = 0;

PVextex-> neighbor = NULL ;;

PVextex-> next = NULL;

Return pVextex;

}

Then we should create an edge,

 

 

LINE * create_new_line (int end, int weight)

{

LINE * pLine = (LINE *) malloc (sizeof (LINE ));

Assert (NULL! = PLine );

PLine-> end = end;

PLine-> weight = weight;

PLine-> next = NULL;

Return pLine;

}

LINE * create_new_line (int end, int weight)

{

LINE * pLine = (LINE *) malloc (sizeof (LINE ));

Assert (NULL! = PLine );

PLine-> end = end;

PLine-> weight = weight;

PLine-> next = NULL;

Return pLine;

} With the above content, it is easy to create a vertex with edges,

 

 

VECTEX * create_new_vectex_for_graph (int start, int end, int weight)

{

VECTEX * pVectex = create_new_vectex (start );

Assert (NULL! = PVectex );

PVectex-> neighbor = create_new_line (end, weight );

Assert (NULL! = PVectex-> neighbor );

Return pVectex;

}

VECTEX * create_new_vectex_for_graph (int start, int end, int weight)

{

VECTEX * pVectex = create_new_vectex (start );

Assert (NULL! = PVectex );

PVectex-> neighbor = create_new_line (end, weight );

Assert (NULL! = PVectex-> neighbor );

Return pVectex;

} So how is it related to graph? In fact, it is not difficult.

 

 

GRAPH * create_new_graph (int start, int end, int weight)

{

GRAPH * pGraph = (GRAPH *) malloc (sizeof (GRAPH ));

Assert (NULL! = PGraph );

 

PGraph-> count = 1;

PGraph-> head = create_new_vectex_for_graph (start, end, weight );

Assert (NULL! = PGraph-> head );

 

Return pGraph;

}

GRAPH * create_new_graph (int start, int end, int weight)

{

GRAPH * pGraph = (GRAPH *) malloc (sizeof (GRAPH ));

Assert (NULL! = PGraph );

 

PGraph-> count = 1;

PGraph-> head = create_new_vectex_for_graph (start, end, weight );

Assert (NULL! = PGraph-> head );

 

Return pGraph;

} With a graph and an edge, it is not difficult to find the node and edge.

 

 

VECTEX * find_vectex_in_graph (VECTEX * pVectex, int start)

{

If (NULL = pVectex)

Return NULL;

 

While (pVectex ){

If (start = pVectex-> start)

Return pVectex;

PVectex = pVectex-> next;

}

 

Return NULL;

}

 

LINE * find_line_in_graph (LINE * pLine, int end)

{

If (NULL = pLine)

Return NULL;

 

While (pLine ){

If (end = pLine-> end)

Return pLine;

 

PLine = pLine-> next;

}

 

Return NULL;

}

VECTEX * find_vectex_in_graph (VECTEX * pVectex, int start)

{

If (NULL = pVectex)

Return NULL;

 

While (pVectex ){

If (start = pVectex-> start)

Return pVectex;

PVectex = pVectex-> next;

}

 

Return NULL;

}

 

LINE * find_line_in_graph (LINE * pLine, int end)

{

If (NULL = pLine)

Return NULL;

 

While (pLine ){

If (end = pLine-> end)

Return pLine;

 

PLine = pLine-> next;

}

 

Return NULL;

}

 

 

 

Summary:

 

(1) The graph is the aggregation of multiple linked lists.

 

(2) If you want to learn a good graph, you 'd better clarify and consolidate the previous linked list and pointer.

 

(3) try to write small functions. Small functions can be built to facilitate reading and debugging.