题目链接

层序遍历

/*
// Definition for a Node.
class Node {public int val;public Node left;public Node right;public Node next;public Node() {}public Node(int _val) {val = _val;}public Node(int _val, Node _left, Node _right, Node _next) {val = _val;left = _left;right = _right;next = _next;}
};
*/class Solution {public Node connect(Node root) {Deque<Node> queue = new LinkedList<Node>();if(root != null){queue.offer(root);}while(!queue.isEmpty()){int size = queue.size();for(int i = 0; i < size; i++){Node node = queue.poll();if(node.left != null){queue.offer(node.left);}if(node.right != null){queue.offer(node.right);}if(i == size - 1){node.next = null;}else{node.next = queue.getFirst();}}}return root;}
}