F - ABCBAC https://atcoder.jp/contests/abc284/tasks/abc284_f

abc284_f.py

class RollingHash:
    def __init__(self, str, base, mod):
        self.base = base
        self.mod = mod
        self.pow = [1] * (len(str) + 1)
        self.hash = [0] * (len(str) + 1)
        for i in range(len(str)):
            self.hash[i + 1] = (self.hash[i] * base + ord(str[i])) % mod
            self.pow[i + 1] = self.pow[i] * base % mod

    def get(self, l, r):
        return (self.hash[r] - self.hash[l] * self.pow[r - l]) % self.mod


base = 128
mod = 998244353
N = int(input())
T = input()
rh = RollingHash(T, base, mod)
rrh = RollingHash(T[::-1], base, mod)
for i in range(N + 1):
    if rh.get(0, i) == rrh.get(N - i, N) and rh.get(N + i, 2 * N) == rrh.get(
        N, 2 * N - i
    ):
        print(T[:i] + T[N + i :])
        print(i)
        break
else:
    print(-1)