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[leetode]Binary Search Tree Iterator

用个stack模拟递归即可

 

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class BSTIterator {public:    BSTIterator(TreeNode *root) {        while(root) {            st.push(root);            root = root->left;        }    }    /** @return whether we have a next smallest number */    bool hasNext() {        return !st.empty();    }    /** @return the next smallest number */    int next() {        TreeNode* top = st.top();        int val = top->val;        st.pop();        top = top->right;        while(top) {            st.push(top);            top = top->left;        }        return val;    }private:    stack<TreeNode*> st;};/** * Your BSTIterator will be called like this: * BSTIterator i = BSTIterator(root); * while (i.hasNext()) cout << i.next(); */

 

[leetode]Binary Search Tree Iterator