二叉树的广义表创建及中序遍历、后序遍历、层次遍历的非递归算法（C语言）

  1 #include<stdio.h>
  2 #include<stdlib.h>
  3 #define M 100
  4 
  5 typedef struct BTREE {
  6 char data;
  7 struct BTREE *lchild, *rchild;
  8 }BT, *LBTREE;
  9 
 10 LBTREE Creat()
 11 {
 12 LBTREE STACK[M], p = NULL, T = NULL;
 13 int flag, top = -1;
 14 char ch;
 15 while (1)
 16 {
 17 scanf_s("%c", &ch);
 18 switch (ch)
 19 {
 20 case ‘(‘:    //左括号则下一个读取字符入栈
 21 STACK[++top] = p;
 22 flag = 1;
 23 break;
 24 case ‘)‘:    //右括号则栈顶元素出栈
 25 top--;
 26 break;
 27 case ‘,‘:
 28 flag = 2;
 29 break;
 30 case ‘@‘:    //返回T，表示创建完毕
 31 return T;
 32 default:    //读到字母时
 33 p = (LBTREE)malloc(sizeof(BT));
 34 p->data = ch;
 35 p->lchild = NULL;
 36 p->rchild = NULL;
 37 if (T == NULL)
 38 T = p;
 39 else if (flag == 1)
 40 STACK[top]->lchild = p;
 41 else if (flag == 2)
 42 STACK[top]->rchild = p;
 43 }
 44 }
 45 }
 46 
 47 void INORDER(LBTREE T)    //中序遍历非递归
 48 {
 49 LBTREE STACK[M], p = T;
 50 int top = -1;
 51 if (T != NULL)
 52 {
 53 do {
 54 while (p != NULL)    //这里不可以是 (p=p->lchild)!=NULL
 55 {
 56 STACK[++top] = p;
 57 p = p->lchild;
 58 }
 59 p = STACK[top--];    //出栈
 60 printf("%c", STACK[top + 1]->data);
 61 p = p->rchild;
 62 } while (!(p == NULL && top == -1));
 63 }
 64 }
 65 
 66 void LAYERORDER(LBTREE T)    //按层次遍历
 67 {
 68 LBTREE QUEUE[M], p;
 69 int front, rear;
 70 if (T != NULL)    //队列
 71 {
 72 QUEUE[0] = T;
 73 front = -1;
 74 rear = 0;
 75 while (front < rear)
 76 {
 77 p = QUEUE[++front];
 78 printf("% c", p->data);
 79 if (p->lchild != NULL)
 80 QUEUE[++rear] = p->lchild;
 81 if (p->rchild != NULL)
 82 QUEUE[++rear] = p->rchild;
 83 
 84 }
 85 }
 86 }
 87 
 88 void POSTORED(LBTREE T)    //后序遍历的非递归算法
 89 {
 90 LBTREE STACK1[M];    //创建了两个栈，一个用来存放结点的地址
 91 int STACK2[M], flag, top = -1;    //另一个用来存放数字，1：可以读取，0：不可读取
 92 LBTREE p = T;
 93 if (T != NULL)
 94 {
 95 do {
 96 while (p != NULL)
 97 {
 98 STACK1[++top] = p;
 99 STACK2[top] = 0;
100 p = p->lchild;
101 }
102 p = STACK1[top];
103 flag = STACK2[top--];
104 if (flag == 0)
105 {
106 STACK1[++top] = p;
107 STACK2[top] = 1;
108 p = p->rchild;
109 }
110 else
111 {
112 printf("%c", p->data);
113 p = NULL;
114 }
115 } while (!(p == NULL && top == -1));
116 }
117 }
118 
119 
120 void Distroyb(LBTREE T)    //销毁二叉树（同样使用递归的方式）
121 {
122 if (T != NULL)
123 {
124 Distroyb(T->lchild);
125 Distroyb(T->rchild);
126 free(T);
127 }
128 }
129 
130 
131 void main(void)
132 {
133 LBTREE T = NULL;
134 puts("输入二叉树数据");    
135 T=Creat(T);
136 
137 puts("按层次遍历输出：");
138 LAYERORDER(T);
139 puts("");
140 
141 puts("非递归中序遍历：");
142 INORDER(T);
143 puts("");
144 
145 puts("非递归后续遍历：");
146 POSTORED(T);
147 
148 Distroyb(T);    //销毁二叉树
149 }