CodeForces E. Binary Numbers AND Sum
http://codeforces.com/contest/1066/problem/E
You are given two huge binary integer numbers aa and bb of lengths nn and mm respectively. You will repeat the following process: if b>0b>0, then add to the answer the value a & ba & b and divide bb by 22 rounding down (i.e. remove the last digit of
The value a & ba & b means bitwise AND of aa and bb. Your task is to calculate the answer modulo 998244353998244353.
Note that you should add the value a & ba & b to the answer in decimal notation, not in binary. So your task is to calculate the answer in decimal notation. For example, if
The first line of the input contains two integers nn and mm (1≤n,m≤2?1051≤n,m≤2?105) — the length of aa and the length of bb correspondingly.
The second line of the input contains one huge integer
The third line of the input contains one huge integer bb. It is guaranteed that this number consists of exactly mm zeroes and ones and the first digit is always 11.
OutputPrint the answer to this problem in decimal notation modulo 998244353998244353.
Examples input Copy4 4output Copy
1010
1101
12input Copy
4 5output Copy
1001
10101
11
代碼:
#include <bits/stdc++.h> using namespace std; typedef long long ll; int N, M; char A[200010], B[200010]; ll sum[200010]; ll Pow(ll x, ll n, ll mod) { ll res = 1; while(n > 0) { if(n % 2 == 1) { res = res * x; res = res % mod; } x = x * x; x = x % mod; n >>= 1; } return res; } int main() { scanf("%d%d", &N, &M); scanf("%s%s", A, B); memset(sum, 0, sizeof(sum)); for(int i = N - 1; i >= 0; i --) { sum[N - 1 - i] =(A[i] - ‘0‘) * Pow(2, N - 1 - i, 998244353) + sum[N - i - 2]; sum[N - 1 - i] %= 998244353; } if(M == 1 && A[N - 1] == ‘1‘) printf("1\n"); else if(M == 1 && A[N - 1] == ‘0‘) printf("0\n"); else { ll ans = 0; for(int i = 0; i <= N / 2 - 1; i ++) swap(A[i], A[N - 1 - i]); for(int i = 0; i <= M / 2 - 1; i ++) swap(B[i], B[M - 1 - i]); for(int i = 0; i < M; i ++) { if(B[i] == ‘1‘) { if(i >= N) sum[i] = sum[N - 1]; ans += sum[i]; ans %= 998244353; } } printf("%I64d\n", ans % 998244353); } return 0; }
CodeForces E. Binary Numbers AND Sum