Phone Screen: Word Search on Straight 8-Direction Lines

Recurring phone-screen prompt. Given a 2D character grid and a target word, decide whether the word appears along any single straight line in 8 directions (up/down/left/right + 4 diagonals). No turns allowed. Follow-ups extend to turning paths and skip-letter matching. Requirements Input: 2D character grid of size R × C, target string word. A match is a straight line of len(word) cells, starting at any cell and moving in one of 8 fixed directions, where the characters read in order equal word. Output: boolean (or list of starting (r, c) matches). Notes Brute force: for each cell, try each of 8 directions; walk len(word) steps, bailing on out-of-bounds or mismatch. Time O(R · C · 8 · L) where L = len(word). Because no turn is allowed, the problem does not require DFS or backtracking; this is the key distinction from LC 79 (Word Search). Follow-up 1 — turns allowed: now becomes classic DFS / backtracking (LC 79), O(R · C · 4^L) worst case. Follow-up 2 — straight line again but characters may be interleaved with arbitrary letters (e.g. "uber" matches "u_b_e_r" on the line, as long as the order is preserved): for each direction, run a two-pointer through the line's characters; total time still O(R · C · max(R, C)) because each cell is the start of at most 8 lines. Preparation Drill LC 79 (Word Search) and LC 212 (Word Search II), then handicap yourself to the no-turn version — fewer cases to track. Pre-write the 8-direction delta array [(-1,-1),(-1,0),(-1,1),(0,-1),(0,1),(1,-1),(1,0),(1,1)] so the round opens with a clean grid template.