先建树可以吗，但是我的程序会崩溃，求帮忙找下错。。尴尬 struct TreeNode { int val; struct TreeNode *left; struct TreeNode *right; TreeNode(int x) : val(x), left(NULL), right(NULL) { } }; void createTree(TreeNode* root, int data){ if (root == NULL){ root = new TreeNode(data); } else if (data < root->val) createTree(root->left, data); else if (data > root->val) createTree(root->right, data); else return; } void pre(TreeNode* root){ if (root){ cout << root->val << " "; pre(root->left); pre(root->right); } } int main(){ int a[100]; int n; TreeNode* root; while (cin >> n){ root = NULL; for (int i = 0; i < n; i++){ cin >> a[i]; createTree(root, a[i]); } pre(root); }     return 0; }