【建立二叉树】后序建立二叉树

来源：互联网发布：图书数据加工人员编辑：程序博客网时间：2024/06/05 05:06

由后序遍历可知，输入顺序是左结点->右结点->子树根结点

比如输入如下树：

/ \

b c

输入序列为 * * * e d * b * * c a $

思路：

使用栈，对左结点和右结点进行压栈；

1.当输入遇到非*，且栈中元素大于等于2，则可以确定一个小三角树形，并将这个树根作为下一个小三角树形的一个子节点；

2.当输入遇到非*，但栈中元素小于2，则直接将此元素压入栈中；

3.当输入遇到*，压入NULL；

4.当输入遇到$，输入结束。

#include <stdio.h>#include <stdlib.h>#include <string.h>typedef struct node{struct node* lc;struct node* rc;int id;}node;typedef struct stack{node **head;node **top;int max;int used;}stack;#define stack_increasement 20#define stack_initsize 10void init_stack(stack *s){s->used = 0;s->head = (node**)malloc(sizeof(node*)*stack_initsize);s->top = s->head;s->max = stack_initsize;}void push_stack(stack *s, node* d){*(s->top++) = d;s->used ++;if(s->used==s->max){s->max+=stack_increasement;s->head = (node**)realloc(s->head, sizeof(node*)*s->max);s->top = s->head+s->used;}}node* pop_stack(stack *s){if(s->used==0)return (node*)-1;s->used --;s->top --;return *(s->top);}void bc(node **T){int input;stack s;node *lctmp, *rctmp;node *temp;init_stack(&s);scanf("%d", &input);while(input!=0){if(input<0){push_stack(&s, NULL);}else{if(s.used>=2){rctmp = pop_stack(&s);lctmp = pop_stack(&s);temp = (node*)malloc(sizeof(node));temp->lc = lctmp;temp->rc = rctmp;temp->id = input;push_stack(&s, temp);}else{temp = (node*)malloc(sizeof(node));temp->lc = NULL;temp->rc = NULL;temp->id = input;push_stack(&s, temp);}}scanf("%d", &input);}*T = pop_stack(&s);}void pre_visit_tree(node *T){  //递归法if(T!=NULL){printf("%d ", T->id);pre_visit_tree(T->lc);pre_visit_tree(T->rc);}else{return;}}int main(void){node *tree;bc(&tree);pre_visit_tree(tree);system("pause");return 0;}

0 0