C++前序遍历（栈）

news2025/11/4 12:34:57

#include <stdio.h>
#include <malloc.h>

//树结构
typedef struct kl
{
   int data;
   struct kl *lchild;
   struct kl *rchild;
}bittree;

//栈结构
typedef struct ji
{
   int top;
   bittree **data;
   int size;
}stack;

//初始化栈
void init(stack *stack,int size)
{
   stack->size = size;
   stack->top = -1;
   stack->data = (bittree**)malloc(size * sizeof(bittree*));
   for(int i = 0 ; i < size ;i++)
   {
       stack->data[i] = NULL;
   }
}

//创建树
bittree *createtree()
{
   bittree *root = NULL;
   int num;
   printf("Please input number:");
   scanf("%d",&num);
   if(num > 0)
   {
       root = (bittree*)malloc(sizeof(bittree));
       root->data = num;
       root->lchild = createtree();
       root->rchild = createtree();
   }
}

//栈的操作判满
int isfull(stack *stack)
{
return stack->top == stack->size-1;
}

//栈的操作判空
int isempty(stack *stack)
{
return stack->top == -1;
}

//栈的操作入栈
void input(stack *stack,bittree *root)
{
   if(isfull(stack)) return;
   stack->top++;
   stack->data[stack->top] = root;
}

//栈的操作出栈
bittree *out(stack *stack)
{
return stack->data[stack->top--];
}

//开始非递归前序排序读出 (中左右)
void previsitbystack1(bittree *root)
{
   stack stack;
   init(&stack,50);

   if(root == NULL)
       return ;

   input(&stack,root);
   while(!isempty(&stack))
   {
       root = out(&stack);
       printf("%5d",root->data);
       if(root->rchild != NULL)
           input(&stack,root->rchild);
       if(root->lchild != NULL)
           input(&stack,root->lchild);
   }
}

void previsitbystack2(bittree *root)
{
   stack stack;
   init(&stack,50);

   if(root == NULL)
       return ;

   while(root != NULL)
   {
       printf("%5d",root->data);
       input(&stack,root);
       root = root->lchild;
   }

   while(!isempty(&stack))
   {
       root = out(&stack);
       if(root->rchild != NULL)
       {
           root = root->rchild;
           while(root != NULL)
           {
               printf("%5d",root->data);
               input(&stack,root);
               root = root->lchild;
           }
       }
   }
}