[145] Binary Tree Postorder Traversal

復健題.......怎麼那麼感人, 修完compile error 就過了....

(痛哭流涕）

**

 * 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().

 */

void postorder(struct TreeNode* root ,int *idx, int* ret){

    if (root == NULL)

        return;

    postorder(root->left, idx, ret);

    postorder(root->right, idx, ret);

    ret[(*idx)++]=root->val;

//printf(" [%d %d]", *idx, root->val);

    return;

}

int* postorderTraversal(struct TreeNode* root, int* returnSize) {

//    if (root == NULL)

//        return;

    int count =0;

    int *ret = calloc(100, sizeof(int));

    postorder(root , &count , ret);

    *returnSize = count;

    return ret;

}