leetcode 94 Binary Tree Inorder Traversal

Given a binary tree, return the inorder traversal of its nodes' values.

For example:
Given binary tree [1,null,2,3],

   1
    \
     2
    /
   3

 

return [1,3,2].

用的递归方法，提示上说递归方法太普通了，尝试用迭代的方法做。(0ms)

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */
/**
 * Return an array of size *returnSize.
 * Note: The returned array must be malloced, assume caller calls free().
 */
void inorder(int *rst,struct TreeNode *root,int *size)
{
    if(root == NULL) return ;
    inorder(rst,root->left,size);
    rst[(*size)++] = root->val;
    inorder(rst,root->right,size);
}
int* inorderTraversal(struct TreeNode* root, int* returnSize) {
    if(root == NULL) return root;
        
    int *rst = malloc(sizeof(int) * 10000);
    if(rst == NULL) return NULL;
    
    *returnSize = 0;
    inorder(rst,root,returnSize);
    
    return rst;
}