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  • 236. Lowest Common Ancestor of a Binary Tree

    Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.

    According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself).”

    Given the following binary tree:  root = [3,5,1,6,2,0,8,null,null,7,4]

     

    Example 1:

    Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1
    Output: 3
    Explanation: The LCA of nodes 5 and 1 is 3.
    

    Example 2:

    Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 4
    Output: 5
    Explanation: The LCA of nodes 5 and 4 is 5, since a node can be a descendant of itself according to the LCA definition.

    普通二叉树,求树中两个节点的最低公共祖先



    C++:
     1 /**
     2  * Definition for a binary tree node.
     3  * struct TreeNode {
     4  *     int val;
     5  *     TreeNode *left;
     6  *     TreeNode *right;
     7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
     8  * };
     9  */
    10 class Solution {
    11 public:
    12     TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
    13         if (root == NULL || root == p || root == q){
    14             return root ;
    15         }
    16         TreeNode* left = lowestCommonAncestor(root->left , p , q) ;
    17         TreeNode* right = lowestCommonAncestor(root->right , p , q) ;
    18         if (left == NULL){
    19             return right ;
    20         }else if (right == NULL){
    21             return left ;
    22         }else{
    23             return root ;
    24         }
    25     }
    26 };
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  • 原文地址:https://www.cnblogs.com/mengchunchen/p/10595896.html
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