struct TreeNode* build(int s, int e, int* inorder, int inorderSize, int* postorder, int* postorderSize) {
    if (s > e) return NULL;
    if ((*postorderSize) < 0) return NULL;
    struct TreeNode* root = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->left = NULL;
    root->right = NULL;
    root->val = *(postorder + (*postorderSize));
    (*postorderSize)--;
    printf("Assigned %d to root.\n", root->val);
    if (s == e) return root;
    int i, index;
    for (i = s; i <= e; i++) {
        if (*(inorder + i) == root->val) {
            index = i;
            break;
        }
    }
    root->right = build(index + 1, e, inorder, inorderSize, postorder, postorderSize);
    root->left = build(s, index - 1, inorder, inorderSize, postorder, postorderSize);
    return root;
}

struct TreeNode* buildTree(int* inorder, int inorderSize, int* postorder, int postorderSize){
   int pIndex = postorderSize - 1;
   return build(0, postorderSize - 1, inorder, inorderSize, postorder, &pIndex);
}