leetcode笔记-zigzag层序遍历

<pre name="code" class="cpp"><pre name="code" class="cpp">zigzag层序遍历</pre>
<pre name="code" class="cpp"></pre><pre name="code" class="cpp">/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
        vector<int> a;
        vector<vector<int>> b;
        stack<TreeNode*> s;
        s.push(root);
        bool right2left=true;
        if(root==NULL) return b;
        else 
        {
            
            while(!s.empty())
            {
               TreeNode *cur;
               stack<TreeNode *> nxtlevel;
               while(!s.empty())
                {
                    TreeNode *cur=s.top();
                    s.pop();
                    a.push_back(cur->val);
                    if(!right2left)
                    {
                        if(cur->left!=NULL) nxtlevel.push(cur->left);
                        if(cur->right!=NULL) nxtlevel.push(cur->right);
                    }
                    else 
                    {
                        if(cur->right!=NULL) nxtlevel.push(cur->right);
                        if(cur->left!=NULL) nxtlevel.push(cur->left);
                    }
                }
                right2left=!right2left;</pre>
               b.push_back(a);
               s=nxtlevel; 
               a.clear(); 
     }
return b; } }};

zigzag层序遍历

</pre><pre name="code" class="cpp">/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
        vector<int> a;
        vector<vector<int>> b;
        stack<TreeNode*> s;
        s.push(root);
        bool right2left=true;
        if(root==NULL) return b;
        else 
        {
            
            while(!s.empty())
            {
               TreeNode *cur;
               stack<TreeNode *> nxtlevel;
               while(!s.empty())
                {
                    TreeNode *cur=s.top();
                    s.pop();
                    a.push_back(cur->val);
                    if(!right2left)
                    {
                        if(cur->left!=NULL) nxtlevel.push(cur->left);
                        if(cur->right!=NULL) nxtlevel.push(cur->right);
                    }
                    else 
                    {
                        if(cur->right!=NULL) nxtlevel.push(cur->right);
                        if(cur->left!=NULL) nxtlevel.push(cur->left);
                    }
                }
                right2left=!right2left;

b.push_back(a); s=nxtlevel; a.clear(); }return b; } }};