LESSON 397 OF 413 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: tr v2 — Set Translation in C#

Practice

Build a more powerful version of the Unix tr command. Given a list of lines and two equal-length strings set1 and set2, replace every character in each line that appears in set1 at index i with set2[i]. Characters not in set1 are unchanged. Return the lines joined by newline characters (\n).

Notes: set1 and set2 have the same length, contain only ASCII characters, and set1 has no repeated character. Characters are taken literally: there are no ranges like a-z. All replacements happen at once, so set1 = "ab", set2 = "ba" swaps the two letters. Lines may be empty.

Function signature:

public string Tr(List<string> lines, string set1, string set2)

Example:

Input: lines = ["banana", "cherry"], set1 = "abc", set2 = "ABC"

Output: "BAnAnA\nCherry"

When printed:
BAnAnA
Cherry

Build a Dictionary<char, char> from each char of set1 to the matching char of set2. Then walk each line and translate via map.ContainsKey(ch) + map[ch].

Dictionary<char, char> map = new Dictionary<char, char>();
for (int i = 0; i < set1.Length; i++) {
    map[set1[i]] = set2[i];
}
// per char: map.ContainsKey(ch) ? map[ch] : ch

The full solution:

class Solution {
    public string Tr(List<string> lines, string set1, string set2) {
        Dictionary<char, char> map = new Dictionary<char, char>();
        for (int i = 0; i < set1.Length; i++) {
            map[set1[i]] = set2[i];
        }
        List<string> result = new List<string>();
        foreach (string line in lines) {
            StringBuilder sb = new StringBuilder();
            for (int j = 0; j < line.Length; j++) {
                char ch = line[j];
                sb.Append(map.ContainsKey(ch) ? map[ch] : ch);
            }
            result.Add(sb.ToString());
        }
        return string.Join("\n", result);
    }
}

STEP 1 OF 11

Guided

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CLI Tool: tr v2 — Set Translation in C#

Tr V2 in C#