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  • 103.Binary Tree Zigzag Level Order Traversal

    /**
     * Definition for binary tree
     * 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<vector<int> >res;
            if (!root) return res;
            stack<TreeNode*> s1;
            stack<TreeNode*> s2;
            s1.push(root);
            vector<int> out;
            while (!s1.empty() || !s2.empty()) {
                while (!s1.empty()) {
                    TreeNode *cur = s1.top();
                    s1.pop();
                    out.push_back(cur->val);
                    if (cur->left) s2.push(cur->left);
                    if (cur->right) s2.push(cur->right);
                } 
                if (!out.empty()) res.push_back(out);
                out.clear();
                while (!s2.empty()) {
                    TreeNode *cur = s2.top();
                    s2.pop();
                    out.push_back(cur->val);
                    if (cur->right) s1.push(cur->right);
                    if (cur->left) s1.push(cur->left);
                }
                if (!out.empty()) res.push_back(out);
                out.clear();
            }
            return res;
        }
    };
    
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  • 原文地址:https://www.cnblogs.com/smallredness/p/10676740.html
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