Submission #153022

#	Time	Username	Problem	Language	Result	Execution time	Memory
153022		arnold518	Boat (APIO16_boat)	C++14	0 / 100	22 ms	14584 KiB

boat

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

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int MAXN = 1000;
const ll MOD = 1e9+7;

int N, S, A[MAXN+10], B[MAXN+10];
vector<int> comp;

ll inv[MAXN+10], bino[MAXN+10][MAXN+10], comb[MAXN+10], f[MAXN+10];
ll dp[MAXN+10][MAXN+10], ans;

int getcomp(int x) { return lower_bound(comp.begin(), comp.end(), x)-comp.begin(); }

ll mypow(ll x, ll y)
{
    if(y==0) return 1;
    if(y%2) return mypow(x, y-1)*x%MOD;
    ll t=mypow(x, y/2);
    return t*t%MOD;
}

int main()
{
    int i, j, k;
    bino[0][0]=1;
    for(i=1; i<=MAXN; i++) for(j=0; j<=i; j++)
    {
        if(j==0 || j==i) bino[i][j]=1;
        else bino[i][j]=(bino[i-1][j]+bino[i-1][j-1])%MOD;
    }

    inv[0]=1;
    for(i=1; i<=MAXN; i++) inv[i]=mypow(i, MOD-2);

    scanf("%d", &N);
    for(i=1; i<=N; i++)
    {
        scanf("%d%d", &A[i], &B[i]);
        B[i]++;
        comp.push_back(A[i]);
        comp.push_back(B[i]);
    }
    comp.push_back(0);
    sort(comp.begin(), comp.end());
    comp.erase(unique(comp.begin(), comp.end()), comp.end());
    S=comp.size()-2;

    ll a=comp[2]-comp[1];

    memset(comb, 0, sizeof(comb)); memset(f, 0, sizeof(f));
    comb[0]=1;
    for(j=1; j<=a; j++) comb[j]=comb[j-1]*(a-j+1)%MOD*inv[j]%MOD;
    for(j=1; j<=N; j++)
    {
        for(k=1; k<=j; k++)
        {
            f[j]+=comb[k]*bino[j-1][k-1]%MOD;
            f[j]%=MOD;
        }
    }

    int cnt=0;
    for(i=1; i<=N; i++)
    {
        if(!(A[i]<=comp[1] && comp[1]<B[i])) continue;
        cnt++;
        dp[i][1]=f[cnt];
    }
    dp[0][1]=1;

    for(i=2; i<=S; i++)
    {
        a=comp[i+1]-comp[i];

        memset(comb, 0, sizeof(comb)); memset(f, 0, sizeof(f));
        comb[0]=1;
        for(j=1; j<=a; j++) comb[j]=comb[j-1]*(a-j+1)%MOD*inv[j]%MOD;
        for(j=1; j<=N; j++)
        {
            for(k=1; k<=j; k++)
            {
                f[j]+=comb[k]*bino[j-1][k-1]%MOD;
                f[j]%=MOD;
            }
        }

        for(j=1; j<=N; j++)
        {
            int cnt=0;
            for(k=j-1; k>=0; k--)
            {
                if(!(A[j]<=comp[i] && comp[i]<B[j])) continue;
                cnt++;
                dp[j][i]+=f[cnt]*dp[k][i-1]%MOD;
                dp[j][i]%=MOD;
            }
            dp[j][i]+=dp[j][i-1]; dp[j][i]%=MOD;
        }
        dp[0][i]=1;
    }
    for(i=1; i<=N; i++) ans+=dp[i][S], ans%=MOD;
    printf("%lld", ans);
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:40:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &N);
     ~~~~~^~~~~~~~~~
boat.cpp:43:14: 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: 0 / 9
• Subtask 2: 0 / 22
• Subtask 3: 0 / 27
• Subtask 4: 0 / 42