前言

提示：记得关注我哦！！！

一、题目

1.二叉树的各种遍历过程及遍历算法设计。

（1）先序遍历二叉树；
（2）中序遍历二叉树；
（3）后序遍历二叉树。

2.实现二叉树各种遍历算法

代码如下（示例）：

#include<stdio.h>
#include<malloc.h>
#define MaxSize 100
typedef char ElemType;
typedef struct node
{ElemType data;struct node *lchild;struct node *rchild;}BTNode;
void CreateBTree(BTNode *&b,char *str)
{BTNode * St[MaxSize],*p;int top=-1,k,j=0;char ch;b=NULL;ch=str[j];while(ch!='\0'){switch(ch){case'(':top++;St[top]=p;k=1;break;case')':top--;break;case',':k=2;break;default:p=(BTNode *)malloc(sizeof(BTNode));p->data=ch;p->lchild=p->rchild=NULL;if(b==NULL)b=p;else{switch(k){case 1:St[top]->lchild=p;break;case 2:St[top]->rchild=p;break;}}}j++;ch=str[j];}
}
void DestroyBTree(BTNode *&b)
{if(b!=NULL){DestroyBTree(b->lchild);DestroyBTree(b->rchild);free(b);}
}
BTNode *FindNode(BTNode *b,ElemType x)
{BTNode *p;if(b==NULL)return NULL;else if(b->data==x)return b;else{p=FindNode(b->lchild,x);if(p!=NULL)return p;elsereturn FindNode(b->rchild,x);}
}
BTNode *LchildNode(BTNode *p)
{return p->lchild;}
BTNode *RchildNode(BTNode *p)
{return p->rchild;
}
int BTHeight(BTNode *b)
{int lchildh,rchildh;if(b==NULL)return(0);else{lchildh=BTHeight(b->lchild);rchildh=BTHeight(b->rchild);return(lchildh>rchildh)?(lchildh+1):(rchildh+1);}
}
void DispBTree(BTNode *b)
{if(b!=NULL){printf("%c",b->data);if(b->lchild!=NULL||b->rchild!=NULL){printf("(");DispBTree(b->lchild);if(b->rchild!=NULL)printf(",");DispBTree(b->rchild);printf(")");}}
}#include"btree.cpp"
void PreOrder(BTNode *b)
{if(b!=NULL){printf("%c",b->data);PreOrder(b->lchild);PreOrder(b->rchild);}
}
void PreOrderl(BTNode *b)
{BTNode *St[MaxSize],*p;int top = -1;if(b!=NULL){top++;St[top]=b;while(top>-1){p=St[top];top--;printf("%c",p->data);if(p->rchild!=NULL){top++;St[top]=p->rchild;}if(p->lchild!=NULL){top++;St[top]=p->lchild;}}printf("\n");}
}
void InOrder(BTNode *b)
{if(b!=NULL){InOrder(b->lchild);printf("%c",b->data);InOrder(b->rchild);}}
void InOrderl(BTNode *b)
{BTNode *St[MaxSize],*p;int top = -1;if(b!=NULL){p=b;while(top>-1 || p!=NULL){while(p!=NULL){top++;St[top]=p;p=p->lchild;}if(top>-1){p=St[top];top--;printf("%c",p->data);p=p->rchild;}}printf("\n");}
}
void PostOrder(BTNode *b)
{if(b!=NULL){PostOrder(b->lchild);PostOrder(b->rchild);printf("%c",b->data);}
}void PostOrderl(BTNode *b)
{BTNode *St[MaxSize],*p;int top = -1;bool flag;if(b!=NULL){do{    while(b!=NULL){ top++;St[top]=p;b=b->lchild;}p=NULL;flag=true;while(top!=-1&&flag){b=St[top];if(b->rchild==p){printf("%c",b->data);top--;p=b;}else{b=b->rchild;flag=false;}}}while(top!=-1);printf("\n");}
}
void TravLevel(BTNode *b)
{BTNode *Qu[MaxSize];int front,rear;front = rear=0;if(b!=NULL)printf("%c",b->data);rear++;Qu[rear]=b;while(rear!=front){front=(front+1)%MaxSize;b=Qu[front];if(b->lchild!=NULL){printf("%c",b->lchild->data);rear=(rear+1)%MaxSize;Qu[rear]=b->lchild;}if(b->rchild!=NULL){printf("%c",b->rchild->data);rear=(rear+1)%MaxSize;Qu[rear]=b->rchild;}}printf("\n");}
int main()
{BTNode *b;CreateBTree(b,"A(B(D,E(H(J,K(L,M(,N))))),C(F,G(,I)))");printf("二叉树b:");DispBTree(b);printf("\n");printf("层次遍历序列:");TravLevel(b);printf("先序遍历序列:\n");printf("   递归算法:");PreOrder(b);printf("\n");printf(" 非递归算法:");PreOrder(b);printf("\n");printf("中序遍历序列:\n");printf("   递归算法:");InOrder(b);printf("\n");printf(" 非递归算法:");InOrder(b);printf("\n");printf("后序遍历序列:\n");printf("   递归算法:");PostOrder(b);printf("\n");printf(" 非递归算法:");PostOrder(b);printf("\n");DestroyBTree(b);return 1;
}