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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */
/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
 //统计节点数
 int countNode(struct TreeNode* root)
 {
    if(root == NULL){
        return 0;
    }else {
        return 1 + countNode(root->left) + countNode(root->right);
    }
 }
 //前序遍历
 void preorder(struct TreeNode* root,int* res,int* index)
 {
    if(root == NULL)return;
    res[*index] = root->val;
    (*index)++;
    preorder(root->left,res,index);
    preorder(root->right,res,index);

 }
 //中序遍历
 void inorder(struct TreeNode* root,int* res,int* index)
{
    if(root== NULL)return;

    inorder(root->left,res,index);
    res[*index] = root->val;
    (*index)++;
    inorder(root->right,res,index);

 }
  //后序遍历
 void postorder(struct TreeNode* root,int* res,int* index)
{
    if(root== NULL)return;

    postorder(root->left,res,index);
    postorder(root->right,res,index);
    res[*index] = root->val;
    (*index)++;
 }
int* Traversal(struct TreeNode* root, int* returnSize) 
{
    //求出返回数组的大小
    *returnSize = countNode(root);
    //用malloc开辟已求出的数组大小
    int* res = (int*)malloc(sizeof(int) * (*returnSize));
    //数组索引初始化
    int index = 0;
    preorder(root,res,&index);
    //inorder(root,res,&index);
    //postorder(root,res,&index);
    return res;

}