smallest-rotation-with-highest-score.py

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

# Given an array A, we may rotate it by a non-negative integer K
# so that the array becomes A[K], A[K+1], A{K+2], ... A[A.length - 1], A[0], A[1], ..., A[K-1].
# Afterward, any entries that are less than or equal to their index are worth 1 point.
#
# For example, if we have [2, 4, 1, 3, 0], and we rotate by K = 2,
# it becomes [1, 3, 0, 2, 4].
# This is worth 3 points because 1 > 0 [no points], 3 > 1 [no points],
# 0 <= 2 [one point], 2 <= 3 [one point], 4 <= 4 [one point].
#
# Over all possible rotations,
# return the rotation index K that corresponds to the highest score we could receive.
# If there are multiple answers, return the smallest such index K.
#
# Example 1:
# Input: [2, 3, 1, 4, 0]
# Output: 3
# Explanation:
# Scores for each K are listed below:
# K = 0,  A = [2,3,1,4,0],    score 2
# K = 1,  A = [3,1,4,0,2],    score 3
# K = 2,  A = [1,4,0,2,3],    score 3
# K = 3,  A = [4,0,2,3,1],    score 4
# K = 4,  A = [0,2,3,1,4],    score 3
# So we should choose K = 3, which has the highest score.
#
# Example 2:
# Input: [1, 3, 0, 2, 4]
# Output: 0
# Explanation:  A will always have 3 points no matter how it shifts.
# So we will choose the smallest K, which is 0.
#
# Note:
# - A will have length at most 20000.
# - A[i] will be in the range [0, A.length].

class Solution(object):
    def bestRotation(self, A):
        """
        :type A: List[int]
        :rtype: int
        """
        N = len(A)
        change = [1] * N
        for i in xrange(N):
            change[(i-A[i]+1)%N] -= 1
        for i in xrange(1, N):
            change[i] += change[i-1]
        return change.index(max(change))