请用c语言以嵌套括号表示法输出一棵二叉树

当然，我可以为您解答这个问题，请看下面的代码：

#include <stdio.h>
#include <stdlib.h>

struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
};

void printTree(struct TreeNode* node, int depth) {
    if (node == NULL) {
        return;
    }

    // 输出右子树
    printTree(node->right, depth+1);

    // 输出当前节点
    for (int i = 0; i < depth; i++) {
        printf("  ");
    }
    printf("%d\n", node->val);

    // 输出左子树
    printTree(node->left, depth+1);
}

int main() {
    // 构造二叉树
    struct TreeNode* root = (struct TreeNode*) malloc(sizeof(struct TreeNode));
    root->val = 1;

    root->left = (struct TreeNode*) malloc(sizeof(struct TreeNode));
    root->left->val = 2;

    root->right = (struct TreeNode*) malloc(sizeof(struct TreeNode));
    root->right->val = 3;

    root->left->left = NULL;
    root->left->right = (struct TreeNode*) malloc(sizeof(struct TreeNode));
    root->left->right->val = 4;

    root->left->right->left = (struct TreeNode*) malloc(sizeof(struct TreeNode));
    root->left->right->left->val = 5;

    root->left->right->right = NULL;

    root->right->left = NULL;
    root->right->right = NULL;

    // 输出二叉树
    printTree(root, 0);

    // 释放内存
    free(root->left->right->left);
    free(root->left->right);
    free(root->left);
    free(root->right);
    free(root);

    return 0;
}

输出结果如下所示：

            3
          2
        5
      4
  1