fancy_sequence.py (1174B)
| # 1622. Fancy Sequence
"""
write an api that generates fancy sequences using the 'append', 'addAll', and
'multAll' operations.
"""
class Fancy:
def __init__(self):
self.a = []
self.add = [0]
self.mult = [1]
self.mod = 10**9 + 7
def append(self, val: int) -> None:
self.a.append(val)
self.add.append(self.add[-1])
self.mult.append(self.mult[-1])
def addAll(self, inc: int) -> None:
self.add[-1] += inc
def multAll(self, m: int) -> None:
self.add[-1] = self.add[-1] * m % self.mod
self.mult[-1] = self.mult[-1] * m % self.mod
def getIndex(self, idx: int) -> int:
if idx >= len(self.a):
return -1
m = self.mult[-1] * pow(self.mult[idx], self.mod - 2, self.mod)
inc = self.add[-1] - self.add[idx] * m
return (self.a[idx] * m + inc) % self.mod
if __name__ == "__main__":
obj = Fancy()
obj.append(2)
obj.addAll(3)
obj.append(7)
obj.multAll(2)
print(obj.getIndex(0))
obj.addAll(3)
obj.append(10)
obj.multAll(2)
print(obj.getIndex(0))
print(obj.getIndex(1))
print(obj.getIndex(2))
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