/*遞迴*/
void func(struct Node* root, int* arr,int* returnSize)
{  
    for (int i=0; i<root->numChildren; i++)
    {
        func(root->children[i],arr,returnSize);        
    }
    arr[(*returnSize)++] = root->val;
}
int* postorder(struct Node* root, int* returnSize) {
    *returnSize=0;
    
 
if (!root) return NULL;
    int* arr = (int*)calloc(10000,sizeof(int));
    func(root,arr,returnSize);
    return arr;
}

/*迭代*/
int* postorder(struct Node* root, int* returnSize) {
    *returnSize=0;
    if (!root) return NULL;
    int* arr = (int*)calloc(10000,sizeof(int));
    struct Node *p, **stack = (struct
 
 Node**)malloc(10000*sizeof(struct Node*));
    int top=-1;
    stack[++top] = root;
    while(top != -1)
    {
        p = stack[top];
        if (p->numChildren == 0)
        {
            arr[(*returnSize)++] = p->val;
            top--;
        }
        while(p->numChildren) stack[++top] = p->children[--(p->numChildren)];
    }
    
 
return arr;
}