제출 #1067085

#제출 시각아이디문제언어결과실행 시간메모리
10670850npataFlooding Wall (BOI24_wall)C++17
12 / 100
189 ms115888 KiB
#include<bits/stdc++.h>
using namespace std;

#define int long long
#define vec vector

const int MOD = 1e9+7;
const int MX = 4;

void add(int& a, int val) {
	a += val;
	a %= MOD;
}

void mul(int& a, int val) {
	a *= val;
	a %= MOD;
}

int32_t main() {
	int N;
	cin >> N;
	vec<int> a(N), b(N);

	for(int i = 0; i<N; i++) {
		cin >> a[i];
	};
	for(int i = 0; i<N; i++) {
		cin >> b[i];
	};


	vec<vec<int>> mxcnt_left(N+2, vec<int>(MX));
	vec<vec<int>> mxcnt_right(N+2, vec<int>(MX));

	mxcnt_left[0][0] = 1;

	for(int i = 1; i<=N; i++) {
		for(int j = 0; j<MX; j++) {
			add(mxcnt_left[i][max(a[i-1], j)], mxcnt_left[i-1][j]);
			add(mxcnt_left[i][max(b[i-1], j)], mxcnt_left[i-1][j]);
		}
	}

	mxcnt_right[N+1][0] = 1;
	for(int i = N; i>=1; i--) {
		for(int j = 0; j<MX; j++) {
			add(mxcnt_right[i][max(a[i-1], j)], mxcnt_right[i+1][j]);
			add(mxcnt_right[i][max(b[i-1], j)], mxcnt_right[i+1][j]);
		}
	}

	vec<vec<int>> mnmx_cnt(N+2, vec<int>(MX));

	for(int i = 1; i<=N; i++) {
		int rightsum = 0;
		for(int j = MX-1; j>=0; j--) {
			add(rightsum, mxcnt_right[i+1][j]);
			add(mnmx_cnt[i][j], (mxcnt_left[i-1][j]*rightsum)%MOD);
		}
		int leftsum = 0;
		for(int j = MX-1; j>=0; j--) {
			add(mnmx_cnt[i][j], (mxcnt_right[i+1][j]*leftsum)%MOD);
			add(leftsum, mxcnt_left[i-1][j]);
		}
	}

	int ans = 0;

	for(int i = 1; i<=N; i++) {
		for(int j = a[i-1]; j<MX; j++) {
			add(ans, mnmx_cnt[i][j]*(j-a[i-1]));
		}
		for(int j = b[i-1]; j<MX; j++) {
			add(ans, mnmx_cnt[i][j]*(j-b[i-1]));
		}
	}

	cout << ans << '\n';
}
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