543. Diameter of Binary Tree
問題描述
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.
解題思路
- 二叉樹的直徑：二叉樹中從一個結點到另一個節點最長的路徑，叫做二叉樹的直徑
- 采用分治和遞歸的思想：根節點為root的二叉樹的直徑 = max(root-left的直徑，root->right的直徑，root->left的最大深度+root->right的最大深度+1)
代碼
// 求二叉樹的直徑 int diameterOfBinaryTree(TreeNode* root) { if(root == nullptr) return 0; int d_l=diameterOfBinaryTree(root->left); int d_r = diameterOfBinaryTree(root->right); int height_l=getHeight(root->left); int height_r=getHeight(root->right); int tmp1=d_l > d_r ? d_l :d_r; int tmp2=height_l+height_r+1; return tmp1>tmp2 ? tmp1 :tmp2; } // 獲得二叉樹的最大深度 int Solution::getHeight(TreeNode* root) { if(root == nullptr) return 0; int h_l=getHeight(root->left); int h_r=getHeight(root->right); return ((h_l > h_r) ? h_l :h_r)+1; }