Maximum Difference Between Node and Ancestor（C++节点与其祖先之间的最大差值）

忘是亡心i 2023-01-05 01:17 80阅读 0赞

解题思路：

（1）保存每个子树中的节点最大值和最小值

/**
     * 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:
        vector<int> dfs(TreeNode *root,int &maxs) {
            if(root==NULL) return {-1,-1};
            vector<int> l=dfs(root->left,maxs);
            vector<int> r=dfs(root->right,maxs);
            
            if(l[0]==-1 && r[0]==-1) return {root->val,root->val};
            else if(l[0]==-1) {
                int root_min = min(r[0],root->val);
                int root_max = max(r[1],root->val);
                int temp = max(abs(root->val-r[0]),abs(root->val-r[1]));
    
                if(temp>maxs) maxs=temp;
                return {root_min,root_max};
            } else if(r[0]==-1) {
                int root_min = min(l[0],root->val);
                int root_max = max(l[1],root->val);
                int temp = max(abs(root->val-l[0]),abs(root->val-l[1]));
    
                if(temp>maxs) maxs=temp;
                return {root_min,root_max};
            } else {
                int root_min = min(min(l[0],r[0]),root->val);
                int root_max = max(max(l[1],r[1]),root->val);
                int temp = max(max(max(abs(root->val-l[0]),abs(root->val-l[1])),abs(root->val-r[0])),abs(root->val-r[1]));
    
                if(temp>maxs) maxs=temp;
                return {root_min,root_max};
            }
        }
        
        int maxAncestorDiff(TreeNode* root) {
            int maxs = 0;
            dfs(root,maxs);
            return maxs;
        }
    };