LED Digit Display Invariant Under 180° Rotation

Onsite coding: given an array of digits 0–9 representing an LED-style display, return whether the rendered display reads identically after a 180° rotation. Equivalent to LeetCode 246 (Strobogrammatic Number) on the digit-string interpretation. Requirements Input: a sequence of digits 0–9 representing the LED display from left to right. Output: true iff the display, rotated 180°, reads as the same sequence. Notes Build a fixed digit-rotation map: 0→0, 1→1, 2→×, 3→×, 4→×, 5→×, 6→9, 7→×, 8→8, 9→6. Any digit mapping to × immediately disqualifies the input. Two-pointer walk from both ends inward: at each step, both left and right digits must be invertible, and rotation[left] == right. Middle character (odd-length): must map to itself (only 0, 1, 8). Watch the digit-vs-character mismatch: if the input is given as integers, no ord() conversion is needed; if it's a string, parse to ints up front. Common follow-up: list all strobogrammatic numbers of length n — recursion that grows the string from both ends with the invertible pair set per level, plus the middle base case. Preparation Memorize the digit rotation map. Practice writing the two-pointer check and the recursive enumeration in the same sit-down — interviewers often ask for both in sequence. Sketch the rotated form of each digit on paper at least once so the mapping survives interview stress.