Compilare: warning: unused import: `HashMap` --> main.rs:1:24 | 1 | use std::collections::{HashMap, HashSet}; | ^^^^^^^ | = note: `#[warn(unused_imports)]` on by default warning: unused variable: `cols` --> main.rs:249:9 | 249 | let cols = grid[0].len(); | ^^^^ help: if this is intentional, prefix it with an underscore: `_cols` | = note: `#[warn(unused_variables)]` on by default warning: 2 warnings emitted