Read a duration a human typed
A config file lets people write timeouts as "1h30m" instead of counting seconds, and the loader has to turn that into a number without trusting it.
- The units are h, m and s. Each may appear at most once, and they must be in that order.
- Each unit is preceded by a run of digits: "2h", "30m", "45s".
- An empty string is zero seconds.
- Anything that does not fit — a stray letter, a number with no unit, units out of order — gives -1.
ParseDuration(text: string) → int
C# needs a compiler and Drill does not host one yet, so this page is the reference rather than an exercise: the problem, worked examples, and the solution in full. To type it out, the same problem runs in Python.
Where you start
public int ParseDuration(string text) {
}Worked examples
| Call | Result |
|---|---|
ParseDuration("1h30m") | 5400 |
ParseDuration("45s") | 45 |
ParseDuration("2h") | 7200 |
ParseDuration("90m") | 5400 |
Hint
Scan digits, then expect exactly one unit letter. Remember which units you have already taken so order and repeats are both caught by the same check.
Reference solution in C#
public int ParseDuration(string text) {
var rank = new Dictionary<char, int> { { 'h', 1 }, { 'm', 2 }, { 's', 3 } };
var mult = new Dictionary<char, int> { { 'h', 3600 }, { 'm', 60 }, { 's', 1 } };
int i = 0, total = 0, last = 0;
while (i < text.Length) {
int n = 0, digits = 0;
while (i < text.Length && char.IsDigit(text[i])) { n = n * 10 + (text[i] - '0'); i++; digits++; }
if (digits == 0 || i >= text.Length) return -1;
char u = text[i];
if (!rank.ContainsKey(u) || rank[u] <= last) return -1;
last = rank[u];
total += n * mult[u];
i++;
}
return total;
}