Recover Binary Search Tree（C++恢复二叉搜索树）

分手后的思念是犯贱 2022-10-12 15:56 151阅读 0赞

（1）递归+性质

/**
     * Definition for a binary tree node.
     * struct TreeNode {
     *     int val;
     *     TreeNode *left;
     *     TreeNode *right;
     *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
     *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
     *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
     * };
     */
    class Solution {
    private:
        vector<int> v;
    public:
        void inorder(TreeNode *root) {
            if(!root) return;
            inorder(root->left);
            v.push_back(root->val);
            inorder(root->right);
            return;
        }
        
        vector<int> find_num() {
            vector<int> vec;
            for(int i=0;i<v.size()-1;i++) {
                if(v[i]>v[i+1]) {
                    if(vec.size()==0) vec.push_back(i);
                    else vec.push_back(i+1);
                }
            }
            return vec;
        }
        
        void helper(vector<int> &vec,TreeNode *root) {
            if(!root) return;
            if(vec.size()==1) {
                if(v[vec[0]]==root->val) root->val=v[vec[0]+1];
                else if(v[vec[0]+1]==root->val) root->val=v[vec[0]];
            } else {
                if(v[vec[0]]==root->val) root->val=v[vec[1]];
                else if(v[vec[1]]==root->val) root->val=v[vec[0]];
            }
            
            helper(vec,root->left);
            helper(vec,root->right);
            return;
        }
        
        void recoverTree(TreeNode* root) {
            inorder(root);
            vector<int> vec=find_num();
            helper(vec,root);
            return;
        }
    };