How do you solve Minimum Money Required Before Transactions on LeetCode?

Minimum Money Required Before Transactions (LeetCode #2412) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n log n) time complexity and O(n) space complexity. Key insight: Transactions with cashback >= cost can be beneficial and should be prioritized.

What is the time complexity of Minimum Money Required Before Transactions?

The optimal solution for Minimum Money Required Before Transactions runs in O(n log n) time and uses O(n) space. The complexity is dominated by the sorting step for the high cashback transactions, making it efficient for large inputs.

What is the brute force solution for Minimum Money Required Before Transactions?

The brute force approach for Minimum Money Required Before Transactions is Brute Force, with O(n!) time complexity and O(n) space complexity. The brute-force approach involves simulating all possible orders of transactions to determine the minimum starting money required. This is straightforward but inefficient as it checks every permutation of transactions. The optimal Optimal Solution approach improves this to O(n log n).

What algorithm or data structure is used to solve Minimum Money Required Before Transactions?

Minimum Money Required Before Transactions uses the following concepts: Array, Greedy, Sorting. The recommended patterns to study are: Greedy Algorithms, Sorting.

What are the interview tips for Minimum Money Required Before Transactions?

Always clarify the problem requirements and constraints before diving into solutions. Think about edge cases, such as all transactions having cashback >= cost. Explain your thought process clearly during the interview to showcase your understanding.

What are common mistakes when solving Minimum Money Required Before Transactions?

Failing to separate transactions correctly based on cashback and cost. Not considering the impact of transaction order on the required starting money.

#2412

Minimum Money Required Before Transactions

Hard

ArrayGreedySortingGreedy AlgorithmsSorting

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n!)	O(n log n)
Space	O(n)	O(n)

💡

Intuition

Time O(n log n)Space O(n)

The optimal approach involves separating transactions into two categories based on cashback. By sorting and calculating the minimum required money efficiently, we can ensure all transactions can be completed regardless of order.

⚙️

Algorithm

3 steps

1Step 1: Split transactions into two lists: one for transactions with cashback >= cost and another for those with cashback < cost.
2Step 2: For the first list, sort transactions by cost in descending order.
3Step 3: Calculate the minimum starting money required by iterating through both lists, adjusting the current money and tracking the maximum money needed.

solution.py26 lines

1# Full working Python code
2def min_money_optimal(transactions):
3    high_cashback = []
4    low_cashback = []
5    for cost, cashback in transactions:
6        if cashback >= cost:
7            high_cashback.append((cost, cashback))
8        else:
9            low_cashback.append((cost, cashback))
10
11    # Sort high cashback transactions by cost descending
12    high_cashback.sort(reverse=True, key=lambda x: x[0])
13    current_money = 0
14    min_money_needed = 0
15
16    # Process high cashback transactions
17    for cost, cashback in high_cashback:
18        current_money += cashback - cost
19        min_money_needed = max(min_money_needed, cost - current_money)
20
21    # Process low cashback transactions
22    for cost, cashback in low_cashback:
23        current_money += cashback - cost
24        min_money_needed = max(min_money_needed, cost - current_money)
25
26    return min_money_needed

ℹ

Complexity note: The complexity is dominated by the sorting step for the high cashback transactions, making it efficient for large inputs.

1Transactions with cashback >= cost can be beneficial and should be prioritized.
2Sorting helps in managing the order of transactions to minimize the required starting money.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.