#1601

Maximum Number of Achievable Transfer Requests

Hard
ArrayBacktrackingBit ManipulationEnumeration
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Approaches

Brute ForceOptimal
Complexity Comparison
Brute ForceOptimal Solution
Time
O(n²)
Space
O(1)
💡

Intuition

Time Space

Instead of checking all combinations, we can use a backtracking approach to explore the requests and keep track of the net changes dynamically. This is like exploring paths in a maze, where we backtrack when we hit a dead end.

⚙️

Algorithm

3 steps
  1. 1Step 1: Use a backtracking function to explore each request.
  2. 2Step 2: Maintain a count of requests that can be fulfilled.
  3. 3Step 3: For each request, either include it in the count or skip it and check the next request.
solution.py20 lines
1def maximumRequests(n, requests):
2    def backtrack(index, count, net_change):
3        nonlocal max_count
4        if index == len(requests):
5            if all(change == 0 for change in net_change):
6                max_count = max(max_count, count)
7            return
8        # Include the current request
9        fr, to = requests[index]
10        net_change[fr] -= 1
11        net_change[to] += 1
12        backtrack(index + 1, count + 1, net_change)
13        net_change[fr] += 1
14        net_change[to] -= 1
15        # Exclude the current request
16        backtrack(index + 1, count, net_change)
17
18    max_count = 0
19    backtrack(0, 0, [0] * n)
20    return max_count

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