代码随想录算法训练营第二十一天|● 530.二叉搜索树的最小绝对差 ● 501.二叉搜索树中的众数 ● 236. 二叉树的最近公共祖先

最新推荐文章于 2025-12-01 22:20:41 发布

原创最新推荐文章于 2025-12-01 22:20:41 发布 · 120 阅读

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#算法

文章介绍了三个关于二叉搜索树的算法：求解最小绝对差，找出节点值的众数，以及找到最近公共祖先。每个算法都涉及到递归遍历和比较操作。

530.二叉搜索树的最小绝对差

class Solution {
public:
int ret=100000;
TreeNode* cur=NULL;
void solve(TreeNode* node){
    if(node==NULL)
    return ;
    solve(node->left);
    if(cur!=NULL){
    if(ret>abs(cur->val-node->val))
    ret=abs(cur->val-node->val);}
    cur=node;
    solve(node->right);
}
    int getMinimumDifference(TreeNode* root) {
     solve(root);
     return ret;   
    }
};

501.二叉搜索树中的众数

class Solution {
public:
    vector<int> ret;
    int count = 0;
    int max = 0;
    TreeNode* cur = NULL;
    void solve(TreeNode* node) {
        if (node == NULL)
            return;
        solve(node->left);
        if (cur == NULL)
            count = 1;
        else if (cur->val == node->val)
            count++;
        else
            count = 1;
        if (count == max)
            ret.push_back(node->val);
        if (count > max) {
            max = count;
            ret.clear();
            ret.push_back(node->val);
        }
        cur = node;
        solve(node->right);
        return;
    }
    vector<int> findMode(TreeNode* root) {
        solve(root);
        return ret;
    }
};

236. 二叉树的最近公共祖先

class Solution {
public:
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
        if (root == NULL)
            return root;
        if (root == p || root == q)
            return root;
        TreeNode* left = lowestCommonAncestor(root->left, p, q);
        TreeNode* right = lowestCommonAncestor(root->right, p, q);
        if (left != NULL && right != NULL)
            return root;
        if (left == NULL && right != NULL) {
            return right;
        } else if (left != NULL && right == NULL)
            return left;
        else
            return NULL;
    }
};