Submission #144805

#	Time	Username	Problem	Language	Result	Execution time	Memory
144805		emilem	Ljetopica (COI19_ljetopica)	C++14	100 / 100	251 ms	63352 KiB

ljetopica

#include <algorithm>
#include <iostream>
#include <vector>
#include <string>
#include <set>
using namespace std;
const long long mod = 1000000007;

long long n, k;
string path, a, b;
vector<long long> pow2(2000);
long long dp[1005][1005][2][2], cnt[1005][1005][2][2];

void Add(long long depth, long long steps, long long ok, long long atBound, long long depth2, long long steps2, long long ok2, long long atBound2, char dir)
{
	if (max(depth, depth2) > n || max(steps, steps2) > k)
		return;
	if (depth == 2 && steps == 0 && ok == 0 && atBound == 1)
		cerr << "";
	dp[depth][steps][ok][atBound] += 2 * dp[depth2][steps2][ok2][atBound2];
	if (dir == 'R')
		dp[depth][steps][ok][atBound] += cnt[depth2][steps2][ok2][atBound2];
	dp[depth][steps][ok][atBound] %= mod;
	cnt[depth][steps][ok][atBound] += cnt[depth2][steps2][ok2][atBound2];
	cnt[depth][steps][ok][atBound] %= mod;
}
long long Solve(string bound)
{
	for (long long depth = 1; depth <= n; ++depth)
		for (long long steps = 0; steps <= k; ++steps)
			for (long long i = 0; i <= 1; ++i)
				for (long long j = 0; j <= 1; ++j)
					cnt[depth][steps][i][j] = dp[depth][steps][i][j] = 0;
	dp[1][0][0][1] = dp[1][0][1][1] = 1;
	cnt[1][0][0][1] = cnt[1][0][1][1] = 1;
	for (long long depth = 1; depth < n; ++depth)
		for (long long steps = 0; steps <= k; ++steps)
			for (long long ok = 0; ok <= 1; ++ok)
			{
				// += dp[][][][0]
				if (depth == 2)
					cerr << "";
				if (path[depth - 1] == (ok ? 'L' : 'R'))
					Add(depth + 1, steps, ok, 0, depth, steps, ok, 0, 'L');
				else
					Add(depth + 1, steps, ok, 0, depth, steps, ok, 0, 'R');
				if (path[depth - 1] == (!ok ? 'L' : 'R'))
					Add(depth + 1, steps + 1, !ok, 0, depth, steps, ok, 0, 'L');
				else
					Add(depth + 1, steps + 1, !ok, 0, depth, steps, ok, 0, 'R');
				// += dp[][][][1]
				if (ok)
				{
					if (path[depth - 1] == 'L')
						Add(depth + 1, steps, ok, bound[depth - 1] == 'R' ? 0 : 1, depth, steps, ok, 1, 'L');
					else if (bound[depth - 1] == 'R')
						Add(depth + 1, steps, ok, 1, depth, steps, ok, 1, 'R');
				}
				else
				{
					if (path[depth - 1] == 'R')
						Add(depth + 1, steps, ok, bound[depth - 1] == 'R' ? 0 : 1, depth, steps, ok, 1, 'L');
					else if (bound[depth - 1] == 'R')
						Add(depth + 1, steps, ok, 1, depth, steps, ok, 1, 'R');
				}
				if (!ok)
				{
					if (path[depth - 1] == 'L')
						Add(depth + 1, steps + 1, !ok, bound[depth - 1] == 'R' ? 0 : 1, depth, steps, ok, 1, 'L');
					else if (bound[depth - 1] == 'R')
						Add(depth + 1, steps + 1, !ok, 1, depth, steps, ok, 1, 'R');
				}
				else
				{
					if (path[depth - 1] == 'R')
						Add(depth + 1, steps + 1, !ok, bound[depth - 1] == 'R' ? 0 : 1, depth, steps, ok, 1, 'L');
					else if (bound[depth - 1] == 'R')
						Add(depth + 1, steps + 1, !ok, 1, depth, steps, ok, 1, 'R');
				}
			}
	/*
	for (long long depth = 1; depth <= n; ++depth)
		for (long long steps = 0; steps <= k; ++steps)
			for (long long i = 0; i <= 1; ++i)
				for (long long j = 0; j <= 1; ++j)
				{
					cout << "dp[" << depth << "][" << steps << "][" << i << "][" << j << "] = " << dp[depth][steps][i][j] << '\t';
					cout << "cnt[" << depth << "][" << steps << "][" << i << "][" << j << "] = " << cnt[depth][steps][i][j] << endl;
				}
	*/
	long long ans = 0;
	for (long long i = 0; i <= 1; ++i)
		for (long long j = 0; j <= 1; ++j)
		{
			ans += dp[n][k][i][j];
			ans %= mod;
		}
	return ans;
}
int main()
{
	pow2[0] = 1;
	for (long long i = 1; i < pow2.size(); ++i)
		pow2[i] = (pow2[i - 1] + pow2[i - 1]) % mod;
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
	cin >> n >> k;
	cin >> path;
	cin >> a >> b;
	reverse(a.begin(), a.end());
	for (long long i = 0; i < a.length(); ++i)
		if (a[i] == '0')
			a[i] = '1';
		else
		{
			a[i] = '0';
			if (i + 1 == a.length())
				a.pop_back();
			break;
		}
	reverse(b.begin(), b.end());
	a.pop_back();
	b.pop_back();
	for (long long i = 0; i < a.length(); ++i)
		a[i] = (a[i] == '0') ? 'L' : 'R';
	for (long long i = 0; i < b.length(); ++i)
		b[i] = (b[i] == '0') ? 'L' : 'R';
	reverse(a.begin(), a.end());
	reverse(b.begin(), b.end());
	cout << (Solve(b) - Solve(a) + mod) % mod << endl;

	char I;
	cin >> I;
}

Compilation message (stderr)

ljetopica.cpp: In function 'int main()':
ljetopica.cpp:103:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (long long i = 1; i < pow2.size(); ++i)
                        ~~^~~~~~~~~~~~~
ljetopica.cpp:112:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (long long i = 0; i < a.length(); ++i)
                        ~~^~~~~~~~~~~~
ljetopica.cpp:118:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (i + 1 == a.length())
        ~~~~~~^~~~~~~~~~~~~
ljetopica.cpp:125:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (long long i = 0; i < a.length(); ++i)
                        ~~^~~~~~~~~~~~
ljetopica.cpp:127:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (long long i = 0; i < b.length(); ++i)
                        ~~^~~~~~~~~~~~

• Subtask 1: 8 / 8
• Subtask 2: 14 / 14
• Subtask 3: 17 / 17
• Subtask 4: 61 / 61