LESSON 379 OF 414 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: head v3 — Cap n at lines.len() in Rust

Practice

Same signature as v2, but now n may be larger than the number of lines. If n > lines.len() simply return all the lines (don't crash, don't pad). For this version assume n ≥ 0. If n is 0, or there are no lines, the result is the empty string.

Function signature:

fn head(lines: Vec<String>, n: i32) -> String

Example:

Input: lines = ["alpha", "beta", "gamma"], n = 10

Output: "alpha\nbeta\ngamma"

When printed:
alpha
beta
gamma

Slicing lines[0..n] past the end panics in Rust, so clamp n with (n as usize).min(lines.len()) before slicing. Rust's [T]::join then stitches the prefix together with newlines.

let end = (n as usize).min(lines.len());
return lines[0..end].join("\n");

The full solution:

impl Solution {
    fn head(lines: Vec<String>, n: i32) -> String {
        let end = (n as usize).min(lines.len());
        return lines[0..end].join("\n");
    }
}

STEP 1 OF 2

Guided

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CLI Tool: head v3 — Cap n at lines.len() in Rust

Head V3 in Rust