LESSON 374 OF 409 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: head v3 — Cap n at lines.size() in C++

Practice

Same signature as v2, but now n may be larger than the number of lines. If n > lines.size() 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:

string head(vector<string> lines, int n)

Example:

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

Output: "alpha\nbeta\ngamma"

When printed:
alpha
beta
gamma

Indexing lines[i] past the end is undefined behavior in C++, so clamp n with min((int)lines.size(), n) before the loop.

int end = min((int)lines.size(), n);
for (int i = 0; i < end; i++) {
    if (i > 0) result += "\n";
    result += lines[i];
}

The full solution:

class Solution {
public:
    string head(vector<string> lines, int n) {
        int end = min((int)lines.size(), n);
        string result;
        for (int i = 0; i < end; i++) {
            if (i > 0) result += "\n";
            result += lines[i];
        }
        return result;
    }
};

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CLI Tool: head v3 — Cap n at lines.size() in C++

Head V3 in C++