Submission #1067117

#	Time	Username	Problem	Language	Result	Execution time	Memory
1067117		0npata	Flooding Wall (BOI24_wall)	C++17	56 / 100	361 ms	237756 KiB

Main

#include<bits/stdc++.h>
using namespace std;

#define int long long
#define vec vector

const int MOD = 1e9+7;
int MX = 1005;

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);

	bool flag = true;
	for(int i = 0; i<N; i++) {
		cin >> a[i];
		flag &= a[i] <=2;
	};
	for(int i = 0; i<N; i++) {
		cin >> b[i];
		flag &= b[i] <=2;
	};
	if(flag) MX = 4;

	set<int> vals;
	for(int i = 0; i<N; i++) {
		vals.insert(a[i]);
		vals.insert(b[i]);
	}
	int id = 0;
	vec<int> id_to_val(MX);
	map<int, int> val_to_id;
	for(int val : vals) {
		val_to_id[val] = id;
		id_to_val[id++] = val;
	}
	for(int i = 0; i<N; i++) {
		a[i] = val_to_id[a[i]];
		b[i] = val_to_id[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]*(id_to_val[j]-id_to_val[a[i-1]]));
		}
		for(int j = b[i-1]; j<MX; j++) {
			add(ans, mnmx_cnt[i][j]*(id_to_val[j]-id_to_val[b[i-1]]));
		}
	}

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

• Subtask 1: 8 / 8
• Subtask 2: 17 / 17
• Subtask 3: 19 / 19
• Subtask 4: 0 / 14
• Subtask 5: 12 / 12
• Subtask 6: 0 / 30