【leetcode】Flatten Binary Tree to Linked List

前序遍歷二叉樹，並進行扁平化處理

#include<iostream>
#include<vector>
#include<deque>
#include<stack>
using namespace std;
struct TreeNode
{
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int val):val(val),left(NULL),right(NULL){};
};

class Solution
{
public:
    TreeNode* fun(TreeNode* root)
    {
        if(!root)
            return NULL;
        stack<TreeNode*>result;
        result.push(root);
        while(!result.empty())
        {
            TreeNode* node=result.top();
            result.pop();
            if(node->right)
                result.push(node->right);
            if(node->left)
                result.push(node->left);
            node->left=NULL;
            if(!result.empty())
            node->right=result.top();
        }
        return root;
    }
};


class Solution3
{
public:
    void fun(TreeNode* root)
    {
        if(!root)
            return;
        vector<TreeNode*>result;
        result.push_back(root);
        while(!result.empty())
        {
            TreeNode* node=result.back();
            result.pop_back();
            if(node->right)
            {
                result.push_back(node->right);
                node->right=NULL;
            }
            if(node->left)
            {
                result.push_back(node->left);
                node->left=NULL;
            }
            if(!result.empty())
                node->right=result.back();
            else
                node->right=NULL;

        }
        while(root)
        {
            cout<<root->val<<' ';
            root=root->right;
        }
    }
};
void main()
{
    TreeNode* node1=new TreeNode(1);
    TreeNode* node2=new TreeNode(2);
    TreeNode* node3=new TreeNode(3);
    TreeNode* node4=new TreeNode(4);
    TreeNode* node5=new TreeNode(5);
    TreeNode* node6=new TreeNode(6);
    TreeNode* node7=new TreeNode(7);
    node1->left=node2;
    node1->right=node3;
    node2->left=node4;
    node2->right=node5;
  /*  node3->left=node6;
    node3->right=node7;*/
   // Solution solution;
    //solution.recoverTree(node1);
    //solution.recover(node1);
    Solution solution;
    TreeNode* head;
    head=solution.fun(node1);
    while(head)
    {
        cout<<head->val<<' ';
        head=head->right;
    }
}