Date: 2026-06-06
Time: 15:52
This file solves LeetCode 1290: Convert Binary Number in a Linked List to Integer. It owns the ListNode definition, the conversion algorithm, a linked-list builder helper, and inline unit tests. It's a self-contained solution module following the repo's standard layout.
ListNode (class)Standard singly-linked list node with val (int) and next (optional pointer). This is the LeetCode-standard definition — it's defined locally rather than imported from a shared module.
min_operations(head) (function)Misleading name — this has nothing to do with "minimum operations." It converts a binary-encoded linked list to its decimal integer value. The head node holds the MSB (most significant bit).
Contract: Accepts an optional ListNode head. Returns an int. Assumes every node's val is 0 or 1.
makelist(values) (function)Test helper that builds a linked list from a Python list of ints. Iterates in reverse to construct the list from tail to head, which is the standard O(n) approach for building a singly-linked list from an array.
TestMinOperations (class)Seven test cases covering: basic examples, single-element lists, all-zeros, a specific 4-bit pattern (1100 = 12), a 30-bit stress test, and leading zeros.
Horner's method — The core algorithm result = result * 2 + node.val is Horner's scheme applied to base-2. Instead of computing positional powers of 2 explicitly, it shifts the accumulator left by one bit and adds the current digit on each step. This is both simpler and avoids needing to know the list length upfront.
Inline tests — Tests live in the same file as the solution and run via unittest.main() when executed directly. The repo also has separate test_solution.py files per problem.
Imports: typing.Optional (for type hints), unittest (for inline tests). No project-internal imports.
Imported by: The "Imported By" list is massive (~400+ test files), which is clearly wrong — those test files don't import *this* solution. That list likely reflects a tooling artifact or cross-reference error. The actual dependent is convert-binary-number-in-a-linked-list-to-integer/test_solution.py.
1. Caller passes the head of a linked list where each node holds 0 or 1 (MSB at head).
2. result starts at 0.
3. For each node: shift result left (multiply by 2), add current bit.
4. Advance to node.next. When None, return result.
For input [1, 0, 1]:
0 * 2 + 1 = 11 * 2 + 0 = 22 * 2 + 1 = 5makelist preserves input order: makelist([1, 0, 1]) produces head→1→0→1→None.head=None) returns 0, which is correct by the loop's no-op behavior.None. The function trusts its input completely — no null checks beyond the natural while node loop guard, no validation of node values. This is standard for LeetCode solutions where inputs are guaranteed well-formed.
convert-binary-number-in-a-linked-list-to-integer/testsolution.py — The companion test file; likely imports minoperations and ListNode from this modulesum-of-root-to-leaf-binary-numbers/solution.py — Same Horner's-method pattern but on a binary tree instead of a linked list; compare the traversal strategiesconvert-binary-number-in-a-linked-list-to-integer/solution.py:min_operations — The function name doesn't match its behavior; worth checking if this naming is a repo-wide pattern or a one-off copy-paste errormiddle-of-the-linked-list/solution.py — Another linked-list problem; check whether ListNode is redefined per-solution or sharedhorner-method-for-binary-conversion — The conversion uses Horner's method (result * 2 + bit), processing MSB-first in a single pass with O(1) spacemin-operations-is-misnamed — The function min_operations performs binary-to-integer conversion, not any "minimum operations" computation; the name doesn't match the problemlistnode-defined-per-solution — ListNode is defined locally in each solution file rather than imported from a shared module, meaning each problem is self-containedempty-list-returns-zero — Passing None as head returns 0 by the natural behavior of the while loop never executing