#include #include struct tree

{

char data;

struct tree *lchild;

struct tree *rchild;

};

typedef struct tree * treptr;

treptr build(treptr t)//先序建树

{

char c;

c=getchar();

if(c=='#')

{

t=NULL;

}

else

{

t=(treptr)malloc(sizeof(struct tree));

t->data=c;

t->lchild=build(t->lchild);

t->rchild=build(t->rchild);

}

return t;

}

#if 0

void postdorder_b(treptr root)//这是前序遍历递归实现

{

if (root!=NULL)

{

printf("%c",root->data);

postdorder(root->lchild);

postdorder(root->rchild);

}

}

void postdorder_m(treptr root)//这是中序遍历递归实现

{

if (root!=NULL)

{

postdorder(root->lchild);

printf("%c",root->data);

postdorder(root->rchild);

}

}

void postdorder_l(treptr root)//这是后序遍历递归实现

{

if (root!=NULL)

{

postdorder(root->lchild);

postdorder(root->rchild);

printf("%c",root->data);

}

}

#endif

struct stack

{

treptr *top,*base;

};

typedef struct stack *stackptr;

void init (stackptr s)//初始化栈

{

s->base=(treptr*)malloc(sizeof(treptr)*100);

s->top=s->base;

}

void push(stackptr s,treptr t)//入栈

{

*(s->top++)=t;

}

treptr pop(stackptr s)//弹出栈顶元素

{

treptr t;

t=*(--(s->top));

return t;

}

treptr gettop(stackptr s)//取栈顶元素

{

treptr *l=s->top-1;

return *(l);

}

void postorder_l(treptr t)//这是非递归后序实现

{

stackptr s=(stackptr)malloc(sizeof(struct stack));

treptr temp=t;

treptr p;

treptr lastvist=NULL;

init(s);

p=t;

while(p||s->top!=s->base)

{

while(p)

{

push(s,p);

p=p->lchild;

}

temp=gettop(s);

if(temp->rchild==NULL||temp->rchild==lastvist)

{

putchar(temp->data);

lastvist=pop(s);

}

else

p=temp->rchild;

}

}

void postorder_m(treptr t)//这是非递归中序实现

{

stackptr s=(stackptr)malloc(sizeof(struct stack));

treptr temp=t;

treptr p;

treptr lastvist=NULL;

init(s);

p=t;

while(p||s->top!=s->base)

{

while(p)

{

push(s,p);

p=p->lchild;

}

temp=pop(s);

putchar(temp->data);

p=temp->rchild;

}

}

void postorder_b(treptr t)//这是非递归前序实现

{

stackptr s=(stackptr)malloc(sizeof(struct stack));

treptr temp=t;

treptr p;

treptr lastvist=NULL;

init(s);

p=t;

while(p||s->top!=s->base)

{

while(p)

{

putchar(p->data);

push(s,p);

p=p->lchild;

}

temp=pop(s);

p=temp->rchild;

}

}

int main()

{

treptr t=NULL;

t=build(t);

//postdorder(t);

printf("\n非递归前序遍历\n");

postorder_b(t);

printf("\n非递归中序遍历\n");

postorder_m(t);

printf("\n非递归后序遍历\n");

postorder_l(t);

printf("\n");

return 0;

}