Leetcode学习笔记：#617. Merge Two Binary Trees

Leetcode学习笔记：#617. Merge Two Binary Trees

Given two binary trees and imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the others are not.

You need to merge them into a new binary tree. The merge rule is that if two nodes overlap, then sum node values up as the new value of the merged node. Otherwise, the NOT null node will be used as the node of new tree.

实现：

public TreeNode mergeTrees(TreeNode t1, TreeNode t2){
	if(t1== null && t2 == null) return null;

	int val = (t1 == null ? 0 : t1.val) + (t2 == null ? 0 : t2.val);
	TreeNode newNode = new TreeNode(val);

	newNode.left = mergeTrees(t1 == null ? null : t1.left, t2 == null ? null : t2.left);
	newNode.right = mergeTrees(t1==null ? null : t1.right, t2 == null? null : t2.rigth);
	return newNode;
}

思路：
递归前序遍历，先从根节点开始，两棵树的节点val相加生成一个新节点，再递归判断和相加剩下的节点