Submission #588613

#	Time	Username	Problem	Language	Result	Execution time	Memory
588613		messiuuuuu	Boat (APIO16_boat)	C++14	100 / 100	474 ms	2392 KiB

boat

#include<bits/stdc++.h>
#define task "C"
#define ll long long
#define ld long double
#define fi first
#define se second
#define pb push_back
using namespace std;
const int MAXN = 1e3 + 5;
const ll INF = 1e18 + 5;
const int MOD = 1e9 + 7;

int n, a[MAXN], b[MAXN];
vector<int> num;

void Input()
{
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        cin >> a[i] >> b[i];
        num.pb(a[i]);
        num.pb(b[i] + 1);
    }
}

int l[MAXN];
int dp[MAXN][MAXN];

void add(int& a, int b)
{
    a += b;
    if (a > MOD)
        a -= MOD;
}

int inv[MAXN];

void Solve()
{
    inv[1] = 1;
    for (int i = 2; i < MAXN; i++)
        inv[i] = 1ll * (MOD - MOD / i) * inv[MOD % i] % MOD;
    sort(num.begin(), num.end());
    num.erase(unique(num.begin(), num.end()), num.end());
    for (int i = 1; i < num.size(); i++)
    {
        l[i] = num[i] - num[i - 1];
    }
    for (int i = 1; i <= n; i++)
    {
        a[i] = upper_bound(num.begin(), num.end(), a[i]) - num.begin();
        b[i] = upper_bound(num.begin(), num.end(), b[i]) - num.begin();
    }
    for (int i = 0; i < num.size(); i++)
        dp[0][i] = 1;
    for (int i = 1; i <= n; i++)
    {
        dp[i][0] = 1;
        for (int j = a[i]; j <= b[i]; j++)
        {
            dp[i][j] = (1ll * dp[i - 1][j - 1] * l[j]) % MOD;
            int cnt = 1;
            int sl = l[j] - 1;
            for (int k = i - 1; k; k--)
            {
                if (a[k] <= j && j <= b[k])
                {
                    cnt++;
                    sl = 1ll * sl * (l[j] + cnt - 2) % MOD * inv[cnt] % MOD;
                    if (!sl)
                        break;
                    add(dp[i][j], 1ll * dp[k - 1][j - 1] * sl % MOD);
                }
            }
        }

        for (int j = 1; j < num.size(); j++)
        {
            add(dp[i][j], (1ll * dp[i - 1][j] + dp[i][j - 1] - dp[i - 1][j - 1] + MOD) % MOD);
        }

    }
    cout << (dp[n][(int)num.size() - 1] - 1 + MOD) % MOD;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    if (fopen(task".INP","r"))
    {
        freopen(task".INP","r",stdin);
        //freopen(task".OUT","w",stdout);
    }
    Input();
    Solve();
}

Compilation message (stderr)

boat.cpp: In function 'void Solve()':
boat.cpp:46:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   46 |     for (int i = 1; i < num.size(); i++)
      |                     ~~^~~~~~~~~~~~
boat.cpp:55:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   55 |     for (int i = 0; i < num.size(); i++)
      |                     ~~^~~~~~~~~~~~
boat.cpp:78:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   78 |         for (int j = 1; j < num.size(); j++)
      |                         ~~^~~~~~~~~~~~
boat.cpp: In function 'int main()':
boat.cpp:93:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   93 |         freopen(task".INP","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 22 / 22
• Subtask 3: 27 / 27
• Subtask 4: 42 / 42