C语言非递归后序遍历二叉树

2020-01-26 13:52:16

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本文实例为大家分享了C语言非递归后序遍历二叉树的具体代码，供大家参考，具体内容如下

法一：实现思路：一个栈先按根->右子树->左子树的顺序访问二叉树。访问时不输出。另一个栈存入前一个栈只进栈的结点。
最后输出后一个栈的结点数据。

#include<stdio.h>#include<stdlib.h>typedef struct TreeNode{  char element;  struct TreeNode *left,*right;}Tree,*BTree;typedef struct StackNode{  BTree data;  struct StackNode *next;}Stack,*PStack;typedef struct{  PStack top; }LinkStack,*PLinkStack;//初始化空栈PLinkStack Init_Stack(void){  PLinkStack S;  S=(PLinkStack)malloc(sizeof(LinkStack));  if(S){    S->top=NULL;  }  return S;}//压栈void Push_Stack(PLinkStack S,BTree T){  PStack p;  p=(PStack)malloc(sizeof(Stack));  p->data=T;  p->next=S->top;  S->top=p;}//判空int empty_Stack(PLinkStack S){  if(S->top){    return 0;  }else{    return 1;  }}//出栈PStack Pop_Stack(PLinkStack S){  PStack q;   if(empty_Stack(S)){    return S->top;  }else{    q=S->top;    S->top=S->top->next;  }  return q;  }//销毁栈void DestroyStack(PLinkStack S){  PStack del;   while(S->top!=NULL){    del=S->top;    S->top=S->top->next;    free(del);  }  free(S);} BTree BuildTree(void){  char ch;  BTree node;  ch=getchar();  if(ch=='#'){    node=NULL;  }else{    node=(BTree)malloc(sizeof(Tree));    node->element=ch;    node->left=BuildTree();    node->right=BuildTree();  }  return node;}void NotRecursionPostOrder(BTree T){  PLinkStack S,CS;  S=Init_Stack();  CS=Init_Stack();  while(T || !empty_Stack(S)){    if(T){      Push_Stack(S,T);      Push_Stack(CS,T);      T=T->right;    }else{      T=Pop_Stack(S)->data;      T=T->left;    }  }  while(CS->top!=NULL){    printf("%c",CS->top->data->element);    CS->top=CS->top->next;  }  DestroyStack(CS);}int main(void){  BTree T;  T=BuildTree();  NotRecursionPostOrder(T);  return 0;}

法二：实现思路。按先序遍历访问每一个结点。存入栈中，当为空时，就出立即栈（第一次出栈）。出栈后应该立即进栈，去访问进栈结点的右结点，这样可以保证先输出左、右结点，再输出根结点。二次进栈利用flag标记。

#include<stdio.h>#include<stdlib.h>typedef struct TreeNode {  char element;  int flag;  struct TreeNode *left, *right;}Tree, *BTree;typedef struct StackNode {  BTree data;  struct StackNode *next;}Stack, *PStack;typedef struct {  PStack top;}LinkStack, *PLinkStack;//初始化空栈PLinkStack Init_Stack(void) {  PLinkStack S = (PLinkStack)malloc(sizeof(LinkStack));  if (S) {    S->top = NULL;  }  return S;}//压栈void Push_Stack(PLinkStack S, BTree T) {  PStack p;  p = (PStack)malloc(sizeof(Stack));  p->data = T;  p->next = S->top;  S->top = p;}//判空int empty_Stack(PLinkStack S) {  if (S->top) {    return 0;  }  else {    return 1;  }}//出栈PStack Pop_Stack(PLinkStack S) {  PStack q = S->top;  S->top = S->top->next;  return q;}BTree BuildTree(void) {  BTree t;  char ch;  ch = getchar();  if (ch == '#') {    t = NULL;  }  else {    t = (BTree)malloc(sizeof(Tree));    t->element = ch;    t->left = BuildTree();    t->right = BuildTree();  }  return t;}void DestroyStack(PLinkStack S){  PStack p;  while(S->top){    p=S->top;    free(p);    S->top=S->top->next;  }} void NotRecursionPostOrder(BTree T) {  PLinkStack S;  S = Init_Stack();  while (T || !empty_Stack(S)) {    if (T) {      T->flag = 0;      Push_Stack(S, T);      T = T->left;    }    else {      T = Pop_Stack(S)->data;      if (T->flag == 0) {        T->flag = 1;        Push_Stack(S, T);        T = T->right;      }      else {        if (T->flag == 1) {          printf("%c", T->element);          T = NULL;        }      }    }  }  DestroyStack(S);//销毁栈 }int main(void) {  BTree T;  T = BuildTree();  NotRecursionPostOrder(T);  return 0;}