Submission #680943

#	Time	Username	Problem	Language	Result	Execution time	Memory
680943		TranGiaHuy1508	Collecting Stamps 3 (JOI20_ho_t3)	C++17	0 / 100	30 ms	67712 KiB

ho_t3

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

void main_program();

signed main(){
	ios_base::sync_with_stdio(0); cin.tie(0);
	main_program();
}

const int inf = 1e9 + 100;

int n, L;
vector<int> dist[2];
vector<int> T;

int dp[205][205][205][2];

int f(int l, int r, int cnt, int lr){
	if (cnt < 0) return -1;
	if (dp[l][r][cnt][lr] > -2) return dp[l][r][cnt][lr];

	int res = inf;
	bool valid = false;

	if (lr == 0){
		if (l > 0){
			int prev1 = f(l-1, r, cnt-1, lr);
			int prev2 = f(l-1, r, cnt, lr);
			int d = dist[0][l] - dist[0][l-1]; d = min(d, L - d);

			if (prev1 >= 0 && prev1 <= T[l] - d){
				valid = true;
				res = min(res, prev1 + d);
			}

			if (prev2 >= 0){
				valid = true;
				res = min(res, prev2 + d);
			}
		}
		if (l > 0){
			int prev1 = f(l-1, r, cnt-1, lr^1);
			int prev2 = f(l-1, r, cnt, lr^1);
			int d = dist[0][l] + dist[1][r]; d = min(d, L - d);

			if (prev1 >= 0 && prev1 <= T[l] - d){
				valid = true;
				res = min(res, prev1 + d);
			}

			if (prev2 >= 0){
				valid = true;
				res = min(res, prev2 + d);
			}
		}
	}
	else{
		if (r < n+1){
			int prev1 = f(l, r+1, cnt-1, lr);
			int prev2 = f(l, r+1, cnt, lr);
			int d = dist[1][r] - dist[1][r+1]; d = min(d, L - d);

			if (prev1 >= 0 && prev1 <= T[r] - d){
				valid = true;
				res = min(res, prev1 + d);
			}

			if (prev2 >= 0){
				valid = true;
				res = min(res, prev2 + d);
			}
		}
		if (r < n+1){
			int prev1 = f(l, r+1, cnt-1, lr^1);
			int prev2 = f(l, r+1, cnt, lr^1);
			int d = dist[0][l] + dist[1][r]; d = min(d, L - d);

			if (prev1 >= 0 && prev1 <= T[r] - d){
				valid = true;
				res = min(res, prev1 + d);
			}

			if (prev2 >= 0){
				valid = true;
				res = min(res, prev2 + d);
			}
		}
	}

	if (!valid) res = -1;
	// if (res >= 0) cout << "dp[" << l << "][" << r << "][" << cnt << "][" << lr << "] = " << res << endl;
	return dp[l][r][cnt][lr] = res;
}

void main_program(){
	cin >> n >> L;

	dist[0].resize(n+2); dist[1].resize(n+2);

	for (int i = 1; i <= n; i++){
		int x; cin >> x;
		dist[0][i] = x;
		dist[1][i] = L - x;
	}

	dist[0][0] = 0; dist[0][n+1] = L;
	dist[1][0] = L; dist[1][n+1] = 0;

	T.resize(n+2);
	for (int i = 1; i <= n; i++) cin >> T[i];

	T[0] = -1; T[n+1] = -1;

	for (int i = 0; i < 205; i++)
		for (int j = 0; j < 205; j++)
			for (int k = 0; k < 205; k++)
				for (int lr = 0; lr < 2; lr++)
					dp[i][j][k][lr] = -2;

	dp[0][n+1][0][0] = dp[0][n+1][0][1] = 0;

	int res = 0;

	for (int i = 0; i <= n+1; i++){
		for (int j = 0; j <= n+1; j++){
			for (int k = 0; k <= n; k++){
				for (int lr = 0; lr < 2; lr++){
					if (f(i, j, k, lr) >= 0) res = max(res, k);
				}
			}
		}
	}

	cout << res << "\n";
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 10
• Subtask 3: 0 / 10
• Subtask 4: 0 / 75