票务售卖Kata测试未返回预期结果求助

Hey there! I see you've got this ticket change kata working in Ruby but hit a snag with your JavaScript implementation—let's fix that. First, let's recap the core requirement to make sure we're on the same page:

Kata需求：电影票单价25美元，需为顾客数组处理找零，若能为所有顾客找零返回"YES"，否则返回"NO"。

Core Logic Breakdown #

The key here is tracking the number of 25$ and 50$ bills we have on hand (100$ bills are useless for giving change, so we don't need to count them). Here's the rule set we need to follow for each customer:

• If a customer pays with 25$: No change needed—just increment our 25$ count.
• If a customer pays with 50$: We need to give back one 25$. If we don't have any, return "NO" immediately. Otherwise, decrement 25$ count and increment 50$ count.
• If a customer pays with 100$: Always prioritize giving back one 50$ + one 25$ first (this preserves more 25$ bills for future 50$ payments). If we don't have that combo, check if we have three 25$ bills. If neither works, return "NO".

Common Pitfalls to Check in Your Code #

Chances are your bug is one of these:

• Trying to use 100$ bills for change (we never do this—only 25$ and 50$ are valid for giving back)
• Handling 100$ payments by using three 25$ bills first (this can leave you short on 25$s for subsequent 50$ customers)
• Incorrectly updating your bill count variables (e.g., forgetting to decrement, or incrementing the wrong one)
• Missing edge cases in your test suite (like a customer paying 50$ as the first person, or a 100$ payment after only two 25$s)

Working JavaScript Implementation (ticketClark.js) #

Here's a clean, tested version of the function:

function tickets(peopleInLine) {
  let count25 = 0;
  let count50 = 0;

  for (const bill of peopleInLine) {
    switch (bill) {
      case 25:
        count25++;
        break;
      case 50:
        if (count25 < 1) return "NO";
        count25--;
        count50++;
        break;
      case 100:
        // Prioritize 50+25 to save 25s for future 50s
        if (count50 >= 1 && count25 >= 1) {
          count50--;
          count25--;
        } else if (count25 >= 3) {
          count25 -= 3;
        } else {
          return "NO";
        }
        break;
      default:
        return "NO"; // Invalid bill amount
    }
  }

  return "YES";
}

module.exports = tickets;

Test Cases (test.js) #

Use these to validate your code (works with Jest or any testing framework):

const tickets = require('./ticketClark');

// Successful scenarios
test('Can handle multiple 25s and a 100', () => {
  expect(tickets([25, 25, 25, 100])).toBe("YES");
});

test('Can handle 25, 25, 50, 100 sequence', () => {
  expect(tickets([25, 25, 50, 100])).toBe("YES");
});

// Failed scenarios
test('Cannot give change for 100 with only one 25', () => {
  expect(tickets([25, 100])).toBe("NO");
});

test('Cannot give change for first customer paying 50', () => {
  expect(tickets([50])).toBe("NO");
});

test('Runs out of 25s after two 100s', () => {
  expect(tickets([25, 25, 25, 100, 100])).toBe("NO");
});

How to Debug Your Existing Code #

Compare your code against this implementation:

1. Check if you're initializing count25 and count50 to 0 (not undefined or some other value)
2. Verify the order of operations for 100$ payments (50+25 first, then three 25s)
3. Make sure you're returning "NO" as soon as you can't give change (don't let the loop continue)

内容的提问来源于stack exchange，提问作者pyan