用C语言实现非递归的方法实现对给定二叉树的先序和层序遍历算法。

先序遍历非递归实现：

void preorderTraversal(TreeNode* root) {
    if (root == NULL) {
        return;
    }
    Stack stack;
    stackInit(&stack);
    stackPush(&stack, root);
    while (!stackIsEmpty(&stack)) {
        TreeNode* node = stackTop(&stack);
        stackPop(&stack);
        printf("%d ", node->val);
        if (node->right != NULL) {
            stackPush(&stack, node->right);
        }
        if (node->left != NULL) {
            stackPush(&stack, node->left);
        }
    }
}

层序遍历非递归实现：

void levelOrderTraversal(TreeNode* root) {
    if (root == NULL) {
        return;
    }
    Queue queue;
    queueInit(&queue);
    queuePush(&queue, root);
    while (!queueIsEmpty(&queue)) {
        int levelSize = queueSize(&queue);
        for (int i = 0; i < levelSize; i++) {
            TreeNode* node = queueFront(&queue);
            queuePop(&queue);
            printf("%d ", node->val);
            if (node->left != NULL) {
                queuePush(&queue, node->left);
            }
            if (node->right != NULL) {
                queuePush(&queue, node->right);
            }
        }
    }
}