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617.merge_two_binary_trees.js
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617.merge_two_binary_trees.js
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/*
* date: 2019-01-07
* author: Level.Z
* source: https://leetcode-cn.com/problems/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.
* Example 1:
* ```
* Input:
* Tree 1 Tree 2
* 1 2
* / \ / \
* 3 2 1 3
* / \ \
* 5 4 7
* Output:
* Merged tree:
* 3
* / \
* 4 5
* / \ \
* 5 4 7
*/
// Definition for a binary tree node.
function TreeNode(val) {
this.val = val;
this.left = this.right = null;
}
/*
* 解法一:递归
*/
const mergeTrees1 = function (t1, t2) {
function _mergeTrees(t1, t2) {
if (!t1 && !t2) return null;
if (!t1 || !t2) return t1 || t2;
let val = t1.val + t2.val;
let node = new TreeNode(val);
node.left = _mergeTrees(t1.left, t2.left);
node.right = _mergeTrees(t1.right, t2.right);
return node;
}
return _mergeTrees(t1, t2);
}