LeetCode 543£º¶þ²æÊ÷µÄÖ±¾¶

class Solution {
public:
    int ans = 0;

    int diameterOfBinaryTree(TreeNode* root) {
        //ans = 1;
        dfs(root);
        return ans;
    }

    int dfs(TreeNode* root) {
        if(!root) return 0;
        int l = dfs(root->left);
        int r = dfs(root->right);
        ans = max(ans, l + r);
        return max(l, r) + 1;
    }
};