Submission #105945

#	Time	Username	Problem	Language	Result	Execution time	Memory
105945		Kastanda	Boat (APIO16_boat)	C++11	100 / 100	373 ms	6648 KiB

boat

#include<bits/stdc++.h>
#define pb push_back
using namespace std;
const int N = 515, Mod = 1e9 + 7;
int n, m, A[N], B[N], dp[N + N][N];
long long F[N + N][N];
pair < int , int > P[N + N];
vector < int > U;
inline void Add(int &a, int b)
{
    a += b;
    if (a >= Mod)
        a -= Mod;
    if (a < 0)
        a += Mod;
}
inline int Power(int a, int b)
{
    int ret = 1;
    for (; b; b >>= 1, a = 1LL * a * a % Mod)
        if (b & 1) ret = 1LL * ret * a % Mod;
    return (ret);
}
int main()
{
    scanf("%d", &n);
    for (int i = 1; i <= n; i++)
    {
        scanf("%d%d", &A[i], &B[i]);
        U.pb(A[i]); U.pb(B[i] + 1);
    }
    U.pb(0); U.pb(1);
    sort(U.begin(), U.end());
    U.resize(unique(U.begin(), U.end()) - U.begin());
    for (int i = 0; i < (int)U.size() - 1; i++)
        P[m ++] = {U[i], U[i + 1] - 1};
    reverse(P, P + m);

    for (int i = 0; i < m; i++)
    {
        int len = P[i].second - P[i].first + 1;
        F[i][0] = len;
        for (int lev = 1; lev <= n; lev ++)
            F[i][lev] = 1LL * F[i][lev - 1] * (len + lev) % Mod * Power(lev + 1, Mod - 2) % Mod;
    }

    for (int i = 0; i <= n; i++)
        dp[m - 1][i] = 1;
    for (int k = 1; k <= n; k ++)
    {
        int sum = 0;
        for (int i = 1; i < m; i ++)
            Add(sum, dp[i][0]);
        for (int i = 0; i < m; i ++, Add(sum, - dp[i][0]))
            if (A[k] <= P[i].first && P[i].second <= B[k])
                for (int j = 0; j <= n; j ++)
                    dp[i][j] = (dp[i][j + 1] + F[i][j] * sum) % Mod;
    }
    int tot = 0;
    for (int i = 0; i < m - 1; i++)
        Add(tot, dp[i][0]);
    return !printf("%d\n", tot);
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:26:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &n);
     ~~~~~^~~~~~~~~~
boat.cpp:29:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d", &A[i], &B[i]);
         ~~~~~^~~~~~~~~~~~~~~~~~~~~~

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