Leetcode-543-Diameter of Binary Tree
543. Diameter of Binary Tree
- Total Accepted: 2826
- Total Submissions: 6539
- Difficulty: Easy
- Contributors: nagasupreeth
Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.
Example:
Given a 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.
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题解：
面对树结构，常理采用recursion。 判断 左边 + 右边 是否最长， 回溯则选择最长的一边。
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
int Search(TreeNode* root, int& ans){
if(root->left==NULL && root->right==NULL){
return 0;
}
int lf = 0;
if(root->left){
lf = Search(root->left, ans) + 1;
}
int rg = 0;
if(root->right){
rg = Search(root->right, ans) + 1;
}
if(lf + rg > ans){
ans = lf + rg;
}
return max(lf,rg);
}
int diameterOfBinaryTree(TreeNode* root) {
int ans = 0;
if(root){
Search(root, ans);
}
return ans;
}
};