LC_1123_LowestCommonAncestorOfDeepestLeaves.cpp

/*
 https://leetcode.com/problems/lowest-common-ancestor-of-deepest-leaves/
*/

/**
 * 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* subtreeWithAllDeepest(TreeNode* root) {
      return solve(root).second;
    }
    
    pair<int, TreeNode*> solve(TreeNode* root)
    {
        if(!root) return {0, nullptr};
        if(!root->left and !root->right) return {1, root};
        auto l = solve(root->left);
        auto r = solve(root->right);
        
        if(l.first == r.first)
            return {l.first+1, root};
        if(l.first > r.first)
            return {l.first+1, l.second};
        else
            return {r.first+1, r.second};
    }
};