hey how are u

Hey! I’m doing good 😊 How are you—what’s up today?

cpp
#include <bits/stdc++.h>
using namespace std;

/*
 * Complete the 'getString' function below.
 * The function is expected to return a STRING.
 * The function accepts STRING input_str as parameter.
 */

string getString(string input_str) {
    vector<int> cnt(26, 0);
    for (char c : input_str) cnt[c - 'a']++;

    vector<bool> inRes(26, false);
    string res;
    res.reserve(26);

    for (char c : input_str) {
        int idx = c - 'a';
        cnt[idx]--;

        if (inRes[idx]) continue; // already kept this character

        // For lexicographically maximum: pop smaller chars if they appear later again
        while (!res.empty() && res.back() < c && cnt[res.back() - 'a'] > 0) {
            inRes[res.back() - 'a'] = false;
            res.pop_back();
        }

        res.push_back(c);
        inRes[idx] = true;
    }

    return res;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    string input_str;
    cin >> input_str;
    cout << getString(input_str) << "\n";
    return 0;
}

Sure — send the schema photos.

While you’re getting those, here’s exactly what this problem is asking (so we’re aligned):

• Output customers with no invoice (never appear in invoice table)
• Output products that were not sold (never appear in invoice line/items table — often called invoice_item, invoice_details, invoice_line, etc.)
• Combine both lists using UNION into one result with columns in this order:

1. a string literal: 'customer' or 'product'
2. the id
3. the name

A typical final query looks like this (I’ll adjust table/column names once I see your schema):

sql
SELECT 'customer' AS type, c.customer_id AS id, c.customer_name AS name
FROM customer c
LEFT JOIN invoice i ON i.customer_id = c.customer_id
WHERE i.invoice_id IS NULL

UNION

SELECT 'product' AS type, p.product_id AS id, p.product_name AS name
FROM product p
LEFT JOIN invoice_item ii ON ii.product_id = p.product_id
WHERE ii.invoice_id IS NULL;

✅ Send the schema images and I’ll rewrite this with the exact correct table names / keys so it passes all test cases.

Yep — the photos are readable. I can clearly see these tables and key columns:

• customer(id PK, customer_name, …)
• product(id PK, product_name, …)
• invoice(id PK, customer_id FK → customer.id, …)
• invoice_item(id PK, invoice_id FK → invoice.id, product_id FK → product.id, …)

Here’s the correct MySQL query (uses UNION and returns columns in the required order):

sql
SELECT
  'customer' AS type,
  c.id       AS id,
  c.customer_name AS name
FROM customer c
WHERE NOT EXISTS (
  SELECT 1
  FROM invoice i
  WHERE i.customer_id = c.id
)

UNION

SELECT
  'product'  AS type,
  p.id       AS id,
  p.product_name AS name
FROM product p
WHERE NOT EXISTS (
  SELECT 1
  FROM invoice_item ii
  WHERE ii.product_id = p.id
);

This lists:

• customers who never appear in invoice
• products that never appear in invoice_item (i.e., never sold)

Answer: 7 ✅