leetcode-94-树题-二叉树的中序遍历

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题目

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解法

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/**
 * 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<int> inorderTraversal(TreeNode* root) {
        vector<int> res;
        inorderTraversalCore(root, res);
        return res;
    }

    // 迭代
    void inorderTraversalCore(TreeNode *root, vector<int> &res){
        stack<TreeNode *> store;
        TreeNode *curr = root;
        while(curr || !store.empty()){
            while(curr){
                store.push(curr);
                curr = curr->left;
            }
            curr = store.top();
            store.pop();
            res.push_back(curr->val);
            curr = curr->right;
        }
    }

    递归
    void inorderTraversalCore(TreeNode *root, vector<int> &res){
        if(!root) return;
        inorderTraversalCore(root->left, res);
        res.push_back(root->val);
        inorderTraversalCore(root->right, res);
    }
};