leetcode/116.populating-next-right-pointers-in-each-node.cpp at master · HouLPcode/leetcode · GitHub

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/*
 * @lc app=leetcode id=116 lang=cpp
 *
 * [116] Populating Next Right Pointers in Each Node
 */
/*
// Definition for a Node.
class Node {
public:
    int val;
    Node* left;
    Node* right;
    Node* next;

    Node() {}

    Node(int _val, Node* _left, Node* _right, Node* _next) {
        val = _val;
        left = _left;
        right = _right;
        next = _next;
    }
};
*/
/*
// Definition for a Node.
class Node {
public:
    int val;
    Node* left;
    Node* right;
    Node* next;

    Node() {}

    Node(int _val, Node* _left, Node* _right, Node* _next) {
        val = _val;
        left = _left;
        right = _right;
        next = _next;
    }
};
*/
// 60 ms, faster than 44.51%
class Solution {
public:
    Node* connect(Node* root) {
        if (root == NULL) {
            return root;
        }
        if (root->left == NULL) { // 没有孩子节点，不用处理
            return root;
        }
        // 前序
        root->left->next = root->right;
        if (root->next != NULL) {
            root->right->next = root->next->left;
        }
        connect(root->left);
        connect(root->right);
        return root;
    }
};