Example 1 · empty
- Arguments
- keys
[]
- Expected return
""
Test data
- Input
[]
- Expected output
""
First unpaired event
First unpaired event
EasyYour task
- A log viewer receives event keys in arrival order.
- Find the first key that appears exactly once after normalization.
- Return that normalized key, or the empty string if no key occurs exactly once.
Required API
- Solve
func Solve(keys []string) string
Behavior
- Normalize only ASCII A–Z to a–z.
- Count every occurrence, even when repeats are far apart.
- Return lowercase and preserve encounter order when choosing the first unique key.
- Leave the input unchanged.
- Separate calls must not share mutable state.
- Use only the standard library.
Constraints
- The input is already valid: 0–1,000 identifiers, each 1–64 ASCII characters long.
- Allowed characters are letters, digits, underscores and hyphens: [A-Za-z0-9_-].
- Do not add parsing, trimming or validation.
Examples
The runner calls your functions directly; you do not need to parse JSON.
Example 2 · one key
- Arguments
- keys
[ "Ping" ]
- Expected return
"ping"
Test data
- Input
["Ping"]
- Expected output
"ping"
Example 3 · normalized frequency
- Arguments
- keys
[ "API", "api", "DB" ]
- Expected return
"db"
Test data
- Input
["API", "api", "DB"]
- Expected output
"db"
Example 4 · none qualifies
- Arguments
- keys
[ "x", "Y", "X", "y" ]
- Expected return
""
Test data
- Input
["x", "Y", "X", "y"]
- Expected output
""
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