C++二叉搜索树代码

代码一，对应力扣二叉搜索树中的检索，代码见下

/**
 * 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 {
public:
    TreeNode* searchBST(TreeNode* root, int val) {
        if(root == NULL){
            return NULL;
        }
        if(root->val < val){
            return searchBST(root->right, val);
        }else if(root->val > val){
            return searchBST(root->left, val);
        }else{
            return root;
        }
    }
};

代码二，对应力扣 二叉搜索树的范围和，代码见下

/**
 * 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 {
public:
    int rangeSumBST(TreeNode* root, int low, int high) {
        if(root == NULL){
            return 0;
        }
        int sum = 0;
        if(root->val >= low && root->val <= high){
            sum += root->val;
        }
        sum += rangeSumBST(root->left, low, high);
        sum += rangeSumBST(root->right, low, high);
        return sum;
    }
};

代码三，将有序数组转化为二叉搜索树，代码见下：

/**
 * 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 {
    TreeNode* sortArray(vector<int>& nums, int l, int r){
        if(l > r){
            return NULL;
        }
        int mid = (l + r)/2;
        TreeNode* node = new TreeNode(nums[mid]);
        node->left = sortArray(nums, l, mid-1);
        node->right = sortArray(nums, mid+1, r);
        return node;

    }
public:
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        return sortArray(nums, 0, nums.size()-1);
    }
};

代码四，对应力扣 验证二叉搜索树，代码见下

/**
 * 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 {
    vector<int> ret;
    void inOrder(TreeNode* root){
        if(root){
            inOrder(root->left);
            ret.push_back(root->val);
            inOrder(root->right);
        }
    }

public:
    bool isValidBST(TreeNode* root) {
        ret.clear();
        inOrder(root);
        for(int i=1; i<ret.size(); ++i){
            if(ret[i] < ret[i-1]){
                return false;
            }
        }
        return true;
    }
};