學習二叉樹時，如果能直觀顯示，測試程序的時候會方便許多。

實現樹形打印的標準方法是利用隊列，此處參考的是CSDN上的一篇文章：樹狀顯示二叉樹， 原程序使用C++實現，這里使用C。

算法中使用了兩個隊列，一個用于存儲樹的結點，另一個用于存儲打印過程中每個結點對應的信息。

上一篇文章寫了可以利用 void 指針來實現模板，這一次嫌麻煩沒有用這個方法，復制粘貼了兩個隊列。

改天試一試能不能把 void 指針的賦值抽象成一套函數來用用。

如同上面那篇文章中介紹的，此打印程序的核心思想是利用父結點的坐標 pos, 和每一層的偏移量 offset 計算左右子結點的位置。

左結點的坐標是 pos - offset, 右結點的坐標是 pos + offset.

實現代碼如下：

1 // content of "BST.h" 2 #include<stdio.h> 3 #include<stdlib.h> 4 5 // definition of the Tree. 6 7 struct Node { 8 int key; 9 struct Node *LeftChild; 10 struct Node *RightChild; 11 }; 12 13 typedef struct Node *Position; 14 typedef struct Node *SearchTree; 15 16 int GetHeight(SearchTree T); 17 SearchTree Insert(SearchTree T, int data); 18 Position Find(SearchTree T, int data); 19 SearchTree Delete(SearchTree T, int data); 20 Position FindMin(SearchTree T); 21 22 void Error1(char *s); 23 24 // Definition of the Queue of Nodes. 25 26 typedef Position ElementType; 27 28 struct Q_Item { 29 ElementType data; 30 struct Q_Item *next; 31 }; 32 33 typedef struct Q_Item *PtrToItem; 34 35 struct Qrec { 36 PtrToItem front, end; 37 }; 38 39 typedef struct Qrec *Queue; 40 41 Queue CreateQ(void); 42 void InQ(Queue Q, ElementType data); 43 ElementType OutQ(Queue Q); 44 void Clear(Queue Q); 45 int IsEmpty(Queue Q); 46 int Power(int x, int n); 47 48 // Definition of the Queue of the info needed in PrintDepth. 49 50 struct infoNode { 51 int pos; 52 int space; 53 int level; 54 int newline; 55 struct infoNode *next; 56 }; 57 58 typedef struct infoNode *infoItem; 59 60 struct infoQrec { 61 infoItem front, end; 62 }; 63 64 typedef struct infoQrec *infoQ; 65 66 infoItem MakeItem(int pos, int space, int level, int newline); 67 infoQ CreateInfoQ(void); 68 void Pushback(infoQ Q, infoItem item); 69 infoItem PopFront(infoQ Q); 70 int InfoQEmpty(infoQ Q); 71 72 // the final function is here 73 75 void PrintDepth_2(SearchTree T);

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1 #include"BST.h" 2 #define TRUE 1 3 #define FALSE 0 4 5 // the Queue of TreeNodes. 6 7 Queue CreateQ(void) 8 { 9 Queue Q = (Queue)malloc(sizeof(struct Qrec)); 10 if(!Q) 11 Error1("out of space for Queue for TreeNode"); 12 13 Q->front = Q->end = NULL; 14 15 return Q; 16 } 17 18 void InQ(Queue Q, ElementType data) 19 { 20 PtrToItem newNode = (PtrToItem)malloc(sizeof(ElementType)); 21 if(!newNode) 22 { 23 printf("no space for newNode\n"); 24 exit(1); 25 } 26 27 newNode->data = data; 28 newNode->next = NULL; 29 30 if(!Q->end) 31 Q->front = Q->end = newNode; 32 else 33 { 34 Q->end->next = newNode; 35 Q->end = newNode; 36 } 37 } 38 39 ElementType OutQ(Queue Q) 40 { 41 ElementType data; 42 PtrToItem temp; 43 44 if(!Q->front) 45 { 46 printf("the Queue is empty\n"); 47 exit(1); 48 } 49 50 temp = Q->front; 51 data = temp->data; 52 53 if(temp->next == NULL) 54 Q->front = Q->end = NULL; 55 else 56 Q->front = temp->next; 57 58 free(temp); 59 60 return data; 61 } 62 63 void Clear(Queue Q) 64 { 65 PtrToItem curr, temp; 66 67 curr = Q->front; 68 69 while(curr) 70 { 71 temp = curr; 72 curr = curr->next; 73 free(temp); 74 } 75 76 free(Q); 77 78 } 79 80 int IsEmpty(Queue Q) 81 { 82 return Q->front == NULL; 83 } 84 85 int Power(int x, int n) 86 { 87 if(n == 0) 88 return 1; 89 else if( n % 2 ) 90 return Power(x*x, n/2) * x; 91 else 92 return Power(x*x, n/2); 93 } 94 95 // the Queue for printing information. 96 97 infoItem MakeItem(int pos, int space, int level, int newline) 98 { 99 infoItem newItem = (infoItem)malloc(sizeof(struct infoNode)); 100 if(!newItem) 101 Error1("out of space for infoNode"); 102 103 newItem->pos = pos; 104 newItem->space = space; 105 newItem->level = level; 106 newItem->newline = newline; 107 newItem->next = NULL; 108 109 return newItem; 110 } 111 112 infoQ CreateInfoQ(void) 113 { 114 infoQ Q = (infoQ)malloc(sizeof(struct infoQrec)); 115 if(!Q) 116 Error1("out of space for infoQ"); 117 118 Q->front = Q->end = NULL; 119 120 return Q; 121 } 122 123 void Pushback(infoQ Q, infoItem item) 124 { 125 infoItem newItem = item; 126 127 if(!Q->end) 128 Q->front = Q->end = newItem; 129 else 130 { 131 Q->end->next = newItem; 132 Q->end = newItem; 133 } 134 } 135 136 infoItem PopFront(infoQ Q) 137 { 138 infoItem item; 139 140 if(!Q->front) 141 Error1("the Queue is empty"); 142 143 item = Q->front; 144 145 if(item->next == NULL) 146 Q->front = Q->end = NULL; 147 else 148 Q->front = item->next; 149 150 return item; 151 } 152 153 void ClearInfoQ(infoQ Q) 154 { 155 infoItem curr, temp; 156 157 curr = Q->front; 158 159 while(curr) 160 { 161 temp = curr; 162 curr = curr->next; 163 free(temp); 164 } 165 166 free(Q); 167 168 } 169 170 int InfoQEmpty(infoQ Q) 171 { 172 return Q->front == NULL; 173 } 174 175 176 177 // this function also print the NULL nodes, 178 // so the tree will look better and prettier, 179 // but also acquire a larger screen because 180 // this function divides the screen into 181 // many blocks, so the space here is consuming. 182 // 183 // | | | |44| | | | 184 // | |29| | | |66| | 185 // |11| |33| |54| |77| 186 // 187 // the key idea of this program is: 188 // while the node is not at the bottom, 189 // no matter if there is a node in the tree, 190 // we create a infoItem with the printing information, 191 // and push a NULL into the Queue. 192 // when we pop the elements out of the Queue, 193 // if the Node it contains is a NULL, we print some 194 // blank block, otherwise we print the key in the Node. 195 196 197 void PrintDepth(SearchTree T) 198 { 199 Position currNode; 200 Queue Q = CreateQ(); 201 infoQ IQ = CreateInfoQ(); 202 infoItem newInfo, currInfo, preInfo; 203 int height = GetHeight(T); 204 int ScreenWidth = Power(2, height+1); 205 int pos, level, space, newline; 206 int dataWidth = 1;　　　　// dataWidth is the width of the block. 207 int i; 208 209 InQ(Q, T); 210 level = 1; 211 pos = ScreenWidth >> level; 212 space = pos; 213 newline = TRUE; 214 215 newInfo = MakeItem(pos, space, level, newline); 216 Pushback(IQ, newInfo); 217 218 preInfo = newInfo; 219 220 while(!IsEmpty(Q)) 221 { 222 currNode = OutQ(Q); 223 currInfo = PopFront(IQ); 224 225 if(currInfo->newline) 226 printf("\n"); 227 228 for(i=0; i<currInfo->space; i++) 229 printf(" "); 230 231 if(currNode) 232 printf("%d",currNode->key); 233 else 234 printf(" "); 235 236 if(currInfo->level < height+1)　　 // if the node is not at the bottom, 237 {　　　　　　　　　　　　　　　　　　 // always create 2 child nodes. 238 level = currInfo->level + 1; 239 pos = currInfo->pos - (ScreenWidth >> level); // the left child. 240 if(level > preInfo->level) 241 { 242 newline = TRUE; 243 space = pos; 244 } 245 else 246 { 247 newline = FALSE; 248 space = pos - preInfo->pos; 249 } 250 251 space--; // set aside space for the data to be printed. 252 newInfo = MakeItem(pos, space, level, newline); 253 254 Pushback(IQ, newInfo); 255 256 preInfo = newInfo; 257 258 if(currNode)　　// if there is a node in a tree, create the left child. 259 { 260 if(currNode->LeftChild) 261 InQ(Q, currNode->LeftChild); 262 else 263 InQ(Q, NULL); 264 } 265 else　　　　　　// if there is a NULL, create the "left child" for NULL. 266 InQ(Q, NULL); 267 268 pos = currInfo->pos + (ScreenWidth >> level); // the right child. 269 newline = FALSE; 270 space = pos - preInfo->pos; 271 space--; 272 273 newInfo = MakeItem(pos, space, level, newline); 274 275 Pushback(IQ, newInfo); 276 277 if(currNode) 278 { 279 if(currNode->RightChild) 280 InQ(Q, currNode->RightChild); 281 else 282 InQ(Q, NULL); 283 } 284 else 285 InQ(Q, NULL); 286 287 preInfo = newInfo; 288 289 } 290 291 } 292 293 printf("\n\n"); 294 }

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轉載于:https://www.cnblogs.com/jeffo/p/print_binary_tree.html

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