Find the longest subarray with distinct entries - EPI

Find the longest subarray with distinct entries

longest-subarray-with-distinct-entries.cc LongestSubarrayWithDistinctEntries.java
public static int longestSubarrayWithDistinctEntries(List<Integer> A) {
  // Records the last occurrences of each entry.
  Map<Integer, Integer> lastOccurrence = new HashMap<>();
  int startingIdx = 0, ans = 0;
  for (int i = 0; i < A.size(); ++i) {
    Integer result = lastOccurrence.put(A.get(i), i);
    if (result != null) { // A[i] appeared before. Check its validity.
      if (result >= startingIdx) {
        ans = Math.max(ans, i - startingIdx);
        startingIdx = result + 1;
      }
    }
  }
  ans = Math.max(ans, A.size() - startingIdx);
  return ans;
}