霍夫曼樹卡在最後一個非內部節點

Question

所以我做了一個函數來建立一個霍夫曼樹，它是按照頻率遞增的順序傳遞一個鏈表（在每個節點內分配一個值），但它似乎卡住時直到最後一個'非內部節點'，就像鏈接列表中的一個節點，該鏈接列表中有一個字符開頭。

void build_tree(pqueue *list) 
{ 

node *temp; 
node* parent_node; 
int min_1, min_2, ind = 0, counter = 0, length = 4; 
temp = new_node(); 


    while (length > 2) 
    { 
     temp = list -> start;   /* 0. point temp at the linked list start (lowest frequency/letter) */ 
     parent_node = new_node();    /* 1. make new node */ 
     min_1 = temp -> frequency;  
     parent_node -> left = temp;   /* 2. assign parent to point at left leaf */ 
     temp = temp -> next;    /* 3. move to next node */ 
     min_2 = temp -> frequency;  
     parent_node -> right = temp;  /* 4. assign parent to point at right leaf */ 
     parent_node -> letter = '$'; 
     parent_node -> frequency = min_1 + min_2; /* 5.assign internal node frequency */ 
     list -> start = temp -> next;/* set the list to point at the next node for the next iteration through the loop */ 

     while (ind == 0 && temp -> next != NULL) 
     { 
      temp = temp -> next; 
      if (temp -> next -> frequency >= parent_node -> frequency && temp != NULL) /* insert parent node */ 
      { 
       parent_node -> next = temp -> next; /* parent points at higher freq node */ 
       temp -> next = parent_node; /* parent node is temp next */ 
       ind = 1; 
      } 
      else if (temp -> next == NULL) /* insert at end of list if parent node is biggest frequency */ 
      { 
       temp -> next = parent_node; 
       ind = 1; 
      } 
     } 
     ind = 0; 
     temp = list -> start; /* temp points at new start (two nodes along)*/ 
     while (temp -> next != NULL) 
     { 
      temp = temp -> next; 
      counter++; 
      printf("%c : %d\n", temp -> letter, temp -> frequency); 
     } 
     printf("----------------------------------------------\n"); 
     length = counter; 
     counter = 0; 
    } 
} 

當傳遞一個文本文件，它會通過建立樹以顯示兩個節點的添加，去除那些節點，並插入新節點的打印每次迭代（相加前兩個節點的頻率），但只有內部節點（標記爲$）和一個非內部節點時，它會以seg故障結束。即這個然而，許多迭代它採取以削減下來到這個數量的節點後：

$ : 4 $ : 4 $ : 4 z: 6 Segmentation fault (core dumped)

Answer 1

那麼，這裏的至少一個錯誤：

while (ind == 0 && temp -> next != NULL) 
{ 
    temp = temp -> next; 
    if (temp -> next -> frequency >= parent_node -> frequency && temp != NULL) /* insert parent node */ 
    { 
     ... 

假設temp->next不NULL，但temp->next->next是NULL。然後你進入循環體，並用temp->next代替temp。所以現在temp->next是NULL。但你試圖參考temp->next->frequencey。這是一個違反分割。核心傾棄。