Hard
Find Products of Elements of Big Array — Python
Full explanation · Time O(q * (logr)^2) · Space O(1)
# Time: O(q * (logr)^2)
# Space: O(1)
# binary search, combinatorics, bitmasks, fast exponentiation
class Solution(object):
def findProductsOfElements(self, queries):
"""
:type queries: List[List[int]]
:rtype: List[int]
"""
def binary_search(left, right, check):
while left <= right:
mid = left + ((right-left)>>1)
if check(mid):
right = mid-1
else:
left = mid+1
return left
def f(x):
def count1(x):
result = i = 0
while 1<<i <= x:
mask = (1<<(i+1))-1
result += ((x&~mask)>>1)+max((x&mask)-(1<<i)+1, 0)
i += 1
return result
def count2(x):
result = i = 0
while 1<<i <= x:
mask = (1<<(i+1))-1
result += (((x&~mask)>>1)+max((x&mask)-(1<<i)+1, 0))*i
i += 1
return result
y = binary_search(1, x-1, lambda i: count1(i) >= x)
result = count2(y-1)
x -= count1(y-1)
i = 0
while 1<<i <= y:
if y&(1<<i):
result += i
x -= 1
if x == 0:
break
i += 1
return result
return [pow(2, f(right+1)-f(left), mod) for left, right, mod in queries]