题目：

题解：

typedef struct TreeNode Node;int method (Node* root, int* max) {if (root == NULL) return 0;int left = method (root->left, max);int right = method (root->right, max);*max = *max > (left + right) ? *max : (left + right);return (left > right ? left : right) + 1;
}int diameterOfBinaryTree(struct TreeNode* root) {int max = 0;method (root, &max);return max;
}