FastPrep
Problem · Hash Table

First Unique Log Entry

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You are given process logs in arrival order. Treat each log as a full string entry.

Return the first log entry that appears exactly once in the entire sequence. If no such log exists, return an empty string.

Function Description

Complete the function findFirstUniqueLog in the editor below.

findFirstUniqueLog has the following parameter:

  1. String[] logs: the process logs in arrival order

Returns

String: the first log whose final frequency is exactly one, or "" if none exists.

Examples
01 · Example 1
logs = ["A", "B", "A", "C", "B"]
return = "C"

A and B each appear twice. C is the first log whose total frequency is exactly one.

02 · Example 2
logs = ["x", "y", "x", "y"]
return = ""

Every log appears more than once, so there is no unique entry.

Constraints
  • 1 <= logs.length <= 10^6
  • Each log entry is treated as an entire string and may contain spaces.
  • The answer is based on the original order among log entries whose final count is exactly one.
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public String findFirstUniqueLog(String[] logs) {
    // write your code here
}
logs["A", "B", "A", "C", "B"]
expected"C"
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