rabbits-in-forest.py

# Time:  O(n)
# Space: O(n)

# In a forest, each rabbit has some color.
# Some subset of rabbits (possibly all of them) tell you how many other rabbits have the same color as them.
# Those answers are placed in an array.
#
# Return the minimum number of rabbits that could be in the forest.
#
# Examples:
# Input: answers = [1, 1, 2]
# Output: 5
# Explanation:
# The two rabbits that answered "1" could both be the same color, say red.
# The rabbit than answered "2" can't be red or the answers would be inconsistent.
# Say the rabbit that answered "2" was blue.
# Then there should be 2 other blue rabbits in the forest that didn't answer into the array.
# The smallest possible number of rabbits in the forest is therefore 5: 3 that answered plus 2 that didn't.
#
# Input: answers = [10, 10, 10]
# Output: 11
#
# Input: answers = []
# Output: 0
#
# Note:
# - answers will have length at most 1000.
# - Each answers[i] will be an integer in the range [0, 999].

class Solution(object):
    def numRabbits(self, answers):
        """
        :type answers: List[int]
        :rtype: int
        """
        count = collections.Counter(answers)
        return sum((((k+1)+v-1)//(k+1))*(k+1) for k, v in count.iteritems())