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LeetCode 24: Swap Nodes in Pairs
link With four pointers (a, b, c, d) we can swap (b, c) in-place. Since head might change, we introduce a dummy node to simplify edge-case handling. Time: , space: .
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LeetCode 1474: Delete N Nodes After M Nodes of a Linked List
link With (prev, curr) pointers, we skip nodes and then delete nodes. Time: , space: .
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LeetCode 725: Split Linked List in Parts
link First we find the expected group sizes from the length of the list and k and then copy the heads of the groups as we do a second pass. Time: , space: .
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LeetCode 2074: Reverse Nodes in Even Length Groups
link Two pass We first collect the groups in a list and then connect the groups. If a group has even size we also reverse it. Time: , space: . One pass For the groups we have two types of operations: If the count of nodes processed by an operation is smaller than the expected…
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LeetCode 92: Reverse Linked List II
link One pass We jump to the left node and reverse (right-left+1) number of nodes. We then fix two pointers: To simplify the (prev, curr) logic we introduce a dummy node. Time: , space: .
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LeetCode 25: Reverse Nodes in k-Group
link Two pass From the length of the list we find how many -groups need to be reversed and we reverse each -group in sequence. While reversing a -group, we have two types of operations: Time: , space: . One pass While reversing a -group, if nodes got reversed where , we know we have…
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Distributed Systems: Consistency Tradeoffs
CAP A partition-tolerant distributed database system continues to work in the face of network partition. Modern distributed database systems are partition-tolerant. In the face of network partition, the system can tradeoff between consistency and availability. When network becomes partitioned, a CP system chooses consistency over availability and an AP system chooses availability over consistency. How…
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LeetCode 621: Task Scheduler
link Note len(tasks)is the lower bound for interval count. If all tasks are distinct, scheduling them in any order achieves the lower bound. However, when some tasks are repeated, we may need to insert idle cycles to cool the CPU down. With repeated tasks, if possible, we should put two instances of the same task…
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LeetCode 253: Meeting Rooms II
link We schedule meetings in order of their start times. If there is a free room, we use it or we declare a new room is required. Say we are trying to schedule the -th meeting and currently there are meeting rooms with earlier meetings scheduled. Which among these rooms would be the most likely…
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LeetCode 759: Employee Free Time
link Pre-sort A single employee’s free times are the gaps between consecutive work intervals. For more than one employees, we can merge overlapping work intervals and have a list of disjoint work intervals across all employees. Then, free times once again would be the gaps between consecutive work intervals. Say there are employees and the…
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unreasonably effective 