二叉树非递归遍历

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树结构

struct TreeNode {    int val;    TreeNode *left;    TreeNode *right;    TreeNode(int x) : val(x), left(NULL), right(NULL) {}};

中序遍历

vector<int> midorderTraversal(TreeNode *root){    vector<int> temp;    stack<TreeNode *> s;        bool left = false;    bool right = false;    if(root == NULL)       return temp;    TreeNode* p = root;       while(p ||!s.empty()){                if(p != NULL){            s.push(p);            p = p->left;        }else{           p = s.top();           temp.push_back(p->val);                     s.pop();           p = p->right;        }    }        vector<int>::const_iterator iter = temp.begin();    while(iter != temp.end()){                cout<<*iter<<"\t";        iter++;    }    cout<<endl;        }

前序遍历

vector<int> preorderTraversal(TreeNode *root)   {          vector<int> temp;         stack<TreeNode *> s;                  s.push(root);                   if (!root) return temp;                   while (!s.empty())          {              TreeNode *p = s.top();              s.pop();              temp.push_back(p->val);              if (p->right) s.push(p->right);              if (p->left) s.push(p->left);          }                 vector<int>::const_iterator iter = temp.begin();        while(iter != temp.end()){               cout<<*iter<<"\t";        iter++;    }    cout<<endl;          return temp;  }

后序遍历

vector<int> postorderTraversal(TreeNode *root)   {     vector<int> temp;    stack<TreeNode *> s;                if(root == NULL)       return temp;        TreeNode *p = root;    s.push(p);        while(!s.empty()){         p = s.top();        s.pop();        temp.insert(temp.begin(),p->val);        if(p->left != NULL) s.push(p->left);        if(p->right != NULL) s.push(p->right);      }        vector<int>::const_iterator iter = temp.begin();    while(iter != temp.end()){               cout<<*iter<<"\t";        iter++;    }    cout<<endl;         }

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