树的遍历总结

树结点定义

typedef struct Node
{
    int value;
    struct Node* left;
    struct Node* right;
    bool visited;
}iNode;

前序遍历的递归和非递归算法

void PreOrder(iNode* r)
{
    if(r==NULL)
        return;
    cout <<r->value<<" ";
    PreOrder(r->left);
    PreOrder(r->right);
}

void Pre_Order(iNode* r)
{
     stack<iNode*> s;
     iNode* tmp=new iNode;
     tmp=r;
     while(tmp!=NULL||!s.empty())
     {
          if(tmp!=NULL)
          {
              cout <<tmp->value<<" ";
              s.push(tmp);
              tmp=tmp->left;
          }
          else
          {
              iNode* node=s.top();
              s.pop();
              tmp=node->right;
          }
     }
}

中序遍历的递归和非递归算法

void MidOrder(iNode* r)
{
    if(r==NULL)
        return;
    MidOrder(r->left);
    cout <<r->value<<" ";
    MidOrder(r->right);
}


void Mid_Order(iNode* r)
{
     stack<iNode*> s;
     iNode* tmp=new iNode;
     tmp=r;
     while(tmp!=NULL||!s.empty())
     {
          if(tmp!=NULL)
          {
               s.push(tmp);
               tmp=tmp->left;
          }
          else
          {
              tmp=s.top();
              s.pop();
              cout <<tmp->value<<" ";
              tmp=tmp->right;
          }
     }     
}

后序遍历的递归和非递归算法

void PostOrder(iNode* r)
{
    if(r==NULL)
        return;
    PostOrder(r->left);
    PostOrder(r->right);
    cout <<r->value<<" ";
}

void Post_Order(iNode* r)
{
     stack<iNode*> s;
     iNode* tmp=new iNode;
     tmp=r;
     while(tmp!=NULL||!s.empty())
     {
          if(tmp!=NULL)
          {
              s.push(tmp);
              tmp=tmp->left;           
          }
          else
          {
              tmp=s.top();
              if(tmp->visited)
              {
                  s.pop();
                  cout <<tmp->value<<" ";
                  tmp=NULL;                  
              }
              else 
              {
                   tmp->visited=true;
                   tmp=tmp->right;                
              }          
          }
     }
}

树的构建，提示行有输入方法

void Tree_Init(iNode* r)
{
    int val;
    int cnt=0;
    queue<iNode*> q;
    cout <<"Enter binary tree elements in level order,put zero if there is no node in corresponding position:";
    while(cin >>val)
    {
        iNode* tmp=new iNode;
        if(val==0)
            tmp=NULL;
        else
        {
            tmp->value=val;
            tmp->visited=false;
        }
        if(q.empty())
        {
            r->value=val;
            r->visited=false;
            q.push(r);
        }
        else
        {
            while(q.front()==NULL)
                q.pop();
            iNode* parent=q.front();
            if(cnt==0)
            {
                parent->left=tmp;
                cnt=1;
            }
            else 
            {
                parent->right=tmp;
                q.pop();
                cnt=0;
            }  
            q.push(tmp);           
        }       
    }
    while(!q.empty())
    {
        iNode* node=q.front();
        if(node!=NULL)
        {
            node->left=NULL;
            node->right=NULL;
        }
        q.pop();
    }
}

测试程序

int main()
{
    iNode *root=new iNode;
    Tree_Init(root);
    cout <<endl<<"The pre order is:";
    PreOrder(root);
    cout <<endl<<"The nonrecursion pre order is:";
    Pre_Order(root);
    cout <<endl<<"The middle order is:";
    MidOrder(root);
    cout <<endl<<"The nonrecursion middle order is:";
    Mid_Order(root);
    cout <<endl<<"The post order is:";
    PostOrder(root);
    cout <<endl<<"The nonrecursion post order is:";
    Post_Order(root);
    system("pause");
    return 0;
}