Short Problem Definition:
Given a table A of N integers from 0 to N-1 calculate the smallest such index P, that that {A[0],…,A[N-1]} = {A[0],…,A[P]}.
Link
Complexity:
expected worst-case time complexity is O(N)
expected worst-case space complexity is O(N)
Execution:
Based on the number of elements that can occur in N, you either mark the occurrences in a boolean array, or put them in a set. The last occurrence of an element that was not seen before is the result.
Solution:
def solution(A):
seen = set()
smallest_prefix_idx = 0
for idx in xrange(len(A)):
if A[idx] not in seen:
seen.add(A[idx])
smallest_prefix_idx = idx
return smallest_prefix_idx