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Brute force · array of node references
▸1given head2collect node refs into nodes[]3L = 0, R = n − 14while L < R: append nodes[L++]5 append nodes[R−−]6relink in that order
state
- goal1 5 2 4 3
Your free access ends in 7 days — and you haven’t tried it yet. Watch one algorithm run, start to finish. It takes about two minutes.
Try one problemGiven the head of a singly linked list, reorder it in place by interleaving nodes from the front and back so the order becomes first, last, second, second-to-last, and so on. Only the node links may be changed, not the values.
▸1given head2collect node refs into nodes[]3L = 0, R = n − 14while L < R: append nodes[L++]5 append nodes[R−−]6relink in that order
line 1Reorder to: first, LAST, second, SECOND-LAST, … — an outside-in weave. The pain: lists cannot walk backward to fetch the tail. Brute fix: collect node references into an array first.