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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.
Input:
Tree 1 Tree 2
1 2
/ \ / \
3 2 1 3
/ \ \
5 4 7
Output:
Merged tree:
3
/ \
4 5
/ \ \
5 4 7Note: The merging process must start from the root nodes of both 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 7Note: The merging process must start from the root nodes of both trees.
思路分析
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/**
* Runtime: 0 ms, faster than 100.00% of Java online submissions for Merge Two Binary Trees.
* Memory Usage: 41.6 MB, less than 22.22% of Java online submissions for Merge Two Binary Trees.
*
* @author D瓜哥 · https://www.diguage.com
* @since 2020-01-29 16:17
*/
public TreeNode mergeTrees(TreeNode t1, TreeNode t2) {
if (Objects.isNull(t1)) {
return t2;
}
if (Objects.isNull(t2)) {
return t1;
}
t1.val += t2.val;
t1.left = mergeTrees(t1.left, t2.left);
t1.right = mergeTrees(t1.right, t2.right);
return t1;
}
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/**
* @author D瓜哥 · https://www.diguage.com
* @since 2024-06-26 16:24:45
*/
public TreeNode mergeTrees(TreeNode t1, TreeNode t2) {
if (t1 == null && t2 == null) {
return null;
}
if (t1 != null && t2 == null) {
return t1;
}
if (t1 == null && t2 != null) {
return t2;
}
TreeNode root = new TreeNode(t1.val + t2.val);
root.left = mergeTrees(t1.left, t2.left);
root.right = mergeTrees(t1.right, t2.right);
return root;
}