پاسخ پرسش اولین زمان رسیدن قورباغه به سمت دیگر رودخانه
def solution(x, a):
covered_time = [-1] * x # Record the time, each position is covered
uncovered = x # Record the number of uncovered position
for index in range(len(a)):
if covered_time[a[index] - 1] != -1:
# This position is already covered
continue
# This position is to be covered
covered_time[a[index] - 1] = index
uncovered -= 1
if uncovered == 0:
# All positions are covered
return index
# Finally, some positions are not covered
return -1