Submission #7548107

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Source Code Expand

import sys
input = sys.stdin.readline
sys.setrecursionlimit(10 ** 7)

import numpy as np

N = int(input())
S = np.array([ord(x) for x in input().rstrip()],dtype=np.int64)

MOD = 10**9 + 7
base = 1234

def cumprod(arr):
    L = len(arr); Lsq = int(L**.5+1)
    arr = np.resize(arr,Lsq**2).reshape(Lsq,Lsq)
    for n in range(1,Lsq):
        arr[:,n] *= arr[:,n-1]; arr[:,n] %= MOD
    for n in range(1,Lsq):
        arr[n] *= arr[n-1,-1]; arr[n] %= MOD
    return arr.ravel()[:L]

x = np.full(N,base,np.int64); x[0] = 1
power = cumprod(x)
x = np.full(N,pow(base,MOD-2,MOD),np.int64); x[0] = 1
power_inv = cumprod(x)

# rolling hash
H = S * power % MOD
Hcum = H.cumsum() % MOD

def test(n):
    # 長さnの文字列で2回現れるものが存在する
    x = (Hcum[n-1:] - Hcum[:N-n+1] + H[:N-n+1]) % MOD
    x *= power_inv[:N-n+1]
    x %= MOD
    # 距離n以上離れたところで連番が存在しないといけない
    ind = x.argsort(kind='stable')
    x = x[ind]
    is_left_end = np.zeros(N-n+1,np.bool)
    is_left_end[1:] = (x[1:] != x[:-1])
    is_left_end[0] = True
    is_right_end = np.zeros(N-n+1,np.bool)
    is_right_end[:-1] = (x[:-1] != x[1:])
    is_right_end[-1] = True
    gap = ind[is_right_end] - ind[is_left_end]
    return gap.max() >= n

left = 0 # 存在
right = N+1 # 非存在
while left + 1 < right:
    mid = (left + right)//2
    if test(mid):
        left = mid
    else:
        right = mid

answer = left
print(answer)

Submission Info

Judge Result