# 算法-二叉树

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### 背景

1. 判断同一颗树，100. Same Tree
 Input:    1         1
/ \       / \
2   3     2   3

[1,2,3],   [1,2,3]

Output: true

2. 判断是否为子树，572. Subtree of Another Tree
Given tree s:

3
/ \
4   5
/ \
1   2
Given tree t:
4
/ \
1   2
Return true, because t has the same structure and node values with a subtree of s.

3. 树的直径，树的两个节点的最大距离，543. Diameter of Binary Tree
       1
/ \
2   3
/ \
4   5

Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].
Note: The length of path between two nodes is represented
by the number of edges between them.

4. 树的路径和，找出所有路径和为给定值得总量 437. Path Sum III

root = [10,5,-3,3,2,null,11,3,-2,null,1], sum = 8

10
/  \
5   -3
/ \    \
3   2   11
/ \   \
3  -2   1
Return 3. The paths that sum to 8 are:
1.  5 -> 3
2.  5 -> 2 -> 1
3. -3 -> 11