二叉树已知前序和中序求后序或者二叉树已知中序和后序求前序已经烂大街了，所以写一下这篇博客
真二叉树：任何一个父节点只要有孩子就必定有左孩子和右孩子
前序遍历 ： 根--左--右
后序遍历：左--右--根
当知道前序遍历和后序
从最底层孩子节点看起，规律为 前右=后右 右为同级右兄弟节点 前左=后右 左为父亲节点，然后将这两个规律循环就可还原此真二叉树代码如下
//目的 实现已知前序和后序的真二叉树还原并求出中序
//思路：前序和后序获得二叉树最底层的左右孩子节点依次往上还原至根从而得到原真二叉树 #include "stdio.h"
#include"stdlib.h"
typedef struct List{int a;struct List* next;struct List* last;struct List* left_child;struct List* right_child;struct List* left_b;struct List* right_b;
} List;typedef struct List_T_B{struct List* top;struct List* bottom;
}List_T_B;
//初始化List链表
List_T_B* init_list(){List* top=(List*)malloc(sizeof(List));List* bottom=(List*)malloc(sizeof(List));top->a=0;top->next=bottom;top->last=NULL;top->left_b=NULL;top->left_child=NULL;top->right_b=NULL;top->right_child=NULL;bottom->a=0;bottom->next=NULL;bottom->last=top;bottom->left_b=NULL;bottom->left_child=NULL;bottom->right_b=NULL;bottom->right_child=NULL;List_T_B* list_st=(List_T_B*)malloc(sizeof(List_T_B));list_st->top=top;list_st->bottom=bottom;return list_st;
}
//插入链表
void insert_list(List* top,int number){List* Create_List=(List*)malloc(sizeof(List));Create_List->a=number;Create_List->left_b=NULL;Create_List->left_child=NULL;Create_List->right_b=NULL;Create_List->right_child=NULL;List* next=top;while(next->next->next!=NULL){next=next->next;}Create_List->next=next->next;Create_List->last=next;next->next->last=Create_List;next->next=Create_List;
}
//确定兄弟节点
void makesure_b(List_T_B* first,List_T_B* bottom){//printf("进入68行\n");List* next_1=first->top;while(next_1->next->next!=NULL){next_1=next_1->next;List* next_2=bottom->top;while(next_2->next->next->next!=NULL){if(next_1->a==next_2->a&&next_1->next->a==next_2->next->a){next_1->right_b=next_1->next;next_1->next=next_1->next->next;next_1->next->last=next_1;next_2->right_b=next_2->next;next_2->next=next_2->next->next;next_2->next->last=next_2;break;}next_2=next_2->next;// printf("%d\n",next_2->a);}// printf("\n");}
}
//确定父节点
void makesure_father(List_T_B* one,List_T_B* two){//printf("进入87行\n");List* next_1=one->bottom;while(next_1->last->last->last!=NULL){if(one->top->next->next->next==NULL){break;}List* next_2=two->top;next_1=next_1->last;while(next_2->next->next!=NULL){if(next_1->a==next_2->a&&next_1->last->a==next_2->next->a){next_1->last->left_child=next_1;next_1->last->right_child=next_1->right_b;next_1->next->last=next_1->last;next_1->last->next=next_1->next;next_2->next->left_child=next_2;next_2->next->right_child=next_2->right_b;next_2->last->next=next_2->next;next_2->next->last=next_2->last;break;}next_2=next_2->next;}}
}
void print_list(List* one,List* two){List* next=one;while(next->next->next!=NULL){printf("%d",next->next->a);next=next->next;}next=two;while(next->next->next!=NULL){printf("%d",next->next->a);next=next->next;}
}
//中序遍历此树
void print_tree(List* one){if(one->left_child!=NULL){print_tree(one->left_child);}printf("%d ",one->a);if(one->right_child!=NULL){print_tree(one->right_child);}}
int main(){//储存先序遍历链表 List_T_B* one=init_list();//储存后序遍历链表 List_T_B* two=init_list();int len,len_1;int sum;printf("请输入列表长度");scanf("%d",&len);printf("请输入先序列表\n");len_1=len;while(len>0){scanf("%d",&sum);insert_list(one->top,sum);len--;}printf("请输入后序列表\n");while(len_1>0){scanf("%d",&sum);insert_list(two->top,sum);len_1--;}while(one->top->next->next->next!=NULL){makesure_b(one,two);makesure_father(one,two);// print_list(one->top,two->top);//system("pause");}printf("输出中序遍历");print_tree(one->top->next);return 0;
}
/*作者：吾非善类
*/