C语言非递归后序遍历二叉树
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; }
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