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C）編寫最小生成樹，涉及創建、挑選和添加過程
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_into_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_into_queue(&pMiniTree->pLine, pDirLine.start, pDirLine.end, pDirLine.weight);
insert_node_into_mini_tree(&pDirLine, pMiniTree);
}
return pMiniTree;
}
d） 構建挑選函數，選擇最合適的邊
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_into_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_into_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）添加節點函數，將尚不是最小生成樹的點納入到最小生成樹當中去
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;
}
注意事項：
（1）d、e是c中調用的子函數，如果大家觀察一下就明白了
（2）最小生成樹是按照自頂向下的順序編寫的，雖然c中的子函數完成了，但是d中還有兩個子函數沒有著落
（3）d中的函數delete_unvalid_line_from_list、sort_for_line_list會在下一篇中繼續介紹
（4）算法只要能夠按照手工計算的流程編寫出來，基本上問題不大，但是一些細節還是要小心注意的
【待續】
