https://h30306.github.io/blog/tags/linked-list/Recent content in Linked-List onHugo -- gohugo.ioenhwork0511@gmail.com (Wei Yi Chung)hwork0511@gmail.com (Wei Yi Chung)© 2026 Wei Yi ChungSun, 01 Nov 2026 00:00:00 +0000https://h30306.github.io/blog/leetcode/leetcode-25/Sun, 01 Nov 2026 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-25/LeetCode 25 note: count the length to know how many full groups to reverse, k nodes each; a dummy head avoids special-casing the first group, and the old group head becomes its tailhttps://h30306.github.io/blog/leetcode/leetcode-328/Sun, 01 Nov 2026 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-328/LeetCode 328 note: build one list from odd positions and one from even positions, then append the even list to the odd one; remember to cut the even list’s tailhttps://h30306.github.io/blog/leetcode/leetcode-146/Sat, 31 Oct 2026 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-146/LeetCode 146 note: a hash map finds nodes and a doubly linked list keeps the usage order; both get and updating an existing key must move the node to the fronthttps://h30306.github.io/blog/leetcode/leetcode-460/Sat, 31 Oct 2026 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-460/LeetCode 460 note: key → node, freq → doubly linked list, plus a min_freq; within the same frequency, LRU decides what to evicthttps://h30306.github.io/blog/algorithm/linked-list/Wed, 21 Oct 2026 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/algorithm/linked-list/Dummy heads, reversal (whole list, a range, half), fast and slow pointers for middles and cycles, two pointers n apart, pairwise swaps, two lists meeting, and copying a list with random pointers via a hash maphttps://h30306.github.io/blog/leetcode/leetcode-23/Tue, 20 Oct 2026 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-23/LeetCode 23 note: a heap that holds only k heads, and divide-and-conquer pairwise merginghttps://h30306.github.io/blog/leetcode/leetcode-21/Sun, 18 Oct 2026 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-21/LeetCode 21 note: the dummy node, and why Python assignment is not a copyhttps://h30306.github.io/blog/leetcode/leetcode-1290/Mon, 14 Jul 2025 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-1290/LeetCode 1290 note: walk head to tail, shifting the running value left by one and adding the new bithttps://h30306.github.io/blog/leetcode/leetcode-2487/Mon, 06 May 2024 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-2487/LeetCode 2487 note: the kept nodes are non-increasing left to right; keep a monotonic stack, pop anything smaller than the new node, then link what remainshttps://h30306.github.io/blog/leetcode/leetcode-92/Sat, 26 Nov 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-92/LeetCode 92 note: walk a dummy to the node before left, then move the following nodes one at a time to just after it, right - left timeshttps://h30306.github.io/blog/leetcode/leetcode-109/Sat, 19 Nov 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-109/LeetCode 109 note: take the middle found with fast and slow pointers as the root and recurse on both halves; the height balances naturallyhttps://h30306.github.io/blog/leetcode/leetcode-116/Fri, 18 Nov 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-116/LeetCode 116 note: in a perfect binary tree, walk each level through the next pointers already set on the level above: left.next = right and right.next = next.left, with O(1) extra spacehttps://h30306.github.io/blog/leetcode/leetcode-117/Fri, 18 Nov 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-117/LeetCode 117 note: connect next pointers level by level with BFS; for a non-perfect tree, looking only at the neighbour’s children breaks the chainhttps://h30306.github.io/blog/leetcode/leetcode-148/Thu, 17 Nov 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-148/LeetCode 148 note: split in half with fast and slow pointers, sort each half recursively and merge; O(n log n) with no extra arrayhttps://h30306.github.io/blog/leetcode/leetcode-142/Mon, 14 Nov 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-142/LeetCode 142 note: after fast and slow meet, send one back to head and step both one at a time; they meet again at the cycle entryhttps://h30306.github.io/blog/leetcode/leetcode-138/Sat, 29 Oct 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-138/LeetCode 138 note: the first pass maps old nodes to new ones, the second wires next and random; seed the dictionary with None -> Nonehttps://h30306.github.io/blog/leetcode/leetcode-143/Sat, 29 Oct 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-143/LeetCode 143 note: find the middle, reverse the second half, and merge the two alternately, cutting the first half’s tailhttps://h30306.github.io/blog/leetcode/leetcode-82/Wed, 26 Oct 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-82/LeetCode 82 note: every duplicated value goes, the head included, so use a dummy; on a duplicate skip to the next different value and link prev.next past ithttps://h30306.github.io/blog/leetcode/leetcode-86/Wed, 26 Oct 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-86/LeetCode 86 note: two dummies collect nodes below x and at least x, then join them, setting the second part’s tail to Nonehttps://h30306.github.io/blog/leetcode/leetcode-61/Sat, 22 Oct 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-61/LeetCode 61 note: count the length and close a ring, take k %= n, walk n - k - 1 steps from the head to the new tail, and break therehttps://h30306.github.io/blog/leetcode/leetcode-24/Fri, 21 Oct 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-24/LeetCode 24 note: a dummy plus pairs, rewiring prev.next, a.next and b.next together; swap nodes, not valueshttps://h30306.github.io/blog/leetcode/leetcode-19/Thu, 20 Oct 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-19/LeetCode 19 note: from a dummy, move fast n + 1 steps ahead, then move both to the end; slow stops before the node to deletehttps://h30306.github.io/blog/leetcode/leetcode-876/Tue, 20 Sep 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-876/LeetCode 876 note: fast moves two steps and slow one; when fast reaches the end slow is in the middle, the right-middle for even lengthshttps://h30306.github.io/blog/leetcode/leetcode-705/Wed, 31 Aug 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-705/LeetCode 705 note: a fixed number of buckets, with the key modulo the bucket count choosing the bucket and a list per bucket handling collisionshttps://h30306.github.io/blog/leetcode/leetcode-234/Mon, 22 Aug 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-234/LeetCode 234 note: find the middle with fast and slow pointers, reverse the second half, and compare from both ends with O(1) extra spacehttps://h30306.github.io/blog/leetcode/leetcode-237/Mon, 22 Aug 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-237/LeetCode 237 note: without the previous node, copy the next node’s value over and delete the next node insteadhttps://h30306.github.io/blog/leetcode/leetcode-203/Sun, 21 Aug 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-203/LeetCode 203 note: the head may be deleted too, so a dummy head turns every deletion into deleting cur.next; do not advance after deletinghttps://h30306.github.io/blog/leetcode/leetcode-206/Sun, 21 Aug 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-206/LeetCode 206 note: three pointers prev / cur / nxt; save the next node, then point cur.next back at prevhttps://h30306.github.io/blog/leetcode/leetcode-141/Sat, 20 Aug 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-141/LeetCode 141 note: Floyd’s cycle detection, fast two steps and slow one; with a cycle they must meet, each advancing from its own positionhttps://h30306.github.io/blog/leetcode/leetcode-160/Sat, 20 Aug 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-160/LeetCode 160 note: each pointer walks its own list then the other’s; both cover lenA + lenB steps and reach the intersection, or None, togetherhttps://h30306.github.io/blog/leetcode/leetcode-83/Wed, 20 Jul 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-83/LeetCode 83 note: sorted, so duplicates are adjacent; skip cur.next while it equals cur, and advance only otherwisehttps://h30306.github.io/blog/leetcode/leetcode-2/Sat, 19 Feb 2022 00:00:00 +0000hwork0511@gmail.com (Wei Yi Chung)https://h30306.github.io/blog/leetcode/leetcode-2/LeetCode 2 note: digits are stored in reverse, so add from the head digit by digit with a carry, looping until both lists end and no carry remains