LeetCode——Diameter of Binary Tree

LeetCode——Diameter of Binary Tree

Question

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.

解题思路

求树的直径意思就是求树的左子树的高度+右子树的高度。 然后遍历所有节点，找到最大值作为直径。

具体实现

class Solution {
public:

    // 左子树的高度+右子树的高度
    int max_height = 0;
    int diameterOfBinaryTree(TreeNode* root) {
        if (!root) {
            return 0;
        }
        int left = height(root->left);
        int right = height(root->right);
        int tmp = left + right;
        if (tmp > max_height)
            max_height = tmp;
        diameterOfBinaryTree(root->left);
        diameterOfBinaryTree(root->right);

        return max_height;
    }

    int height(TreeNode* root) {
        if (!root) {
            return 0;
        }
        else {
            int i = height(root->left);
            int j = height(root->right);
            if (i >= j) {
                return ++i;
            } else {
                return ++j;
            }
        }
    }
};