116.populating-next-right-pointers-in-each-node.cpp

/*
// Definition for a Node.
class Node {
public:
    int val;
    Node* left;
    Node* right;
    Node* next;

    Node() : val(0), left(NULL), right(NULL), next(NULL) {}

    Node(int _val) : val(_val), left(NULL), right(NULL), next(NULL) {}

    Node(int _val, Node* _left, Node* _right, Node* _next)
        : val(_val), left(_left), right(_right), next(_next) {}
};
*/

class Solution {
public:
    Node* connect(Node* root) {
        if(root == NULL) return root;
        Node* root1 = root;
        queue<Node*> q;
        q.push(root1);
        Node* prev;
        while (q.empty() == false)
        {
            int n = q.size();
            Node* curr;
            for(int i=0;i<n;i++){
                curr = q.front();
                q.pop();
                Node *next = q.front();
                curr->next = next;
                if(curr->left != NULL){
                    q.push(curr->left);
                }
                if(curr->right != NULL){
                    q.push(curr->right);
                }
            }
            curr->next = NULL;
        }

        return root;
    }
};