Submission #152816

#	Time	Username	Problem	Language	Result	Execution time	Memory
152816		arnold518	Boat (APIO16_boat)	C++14	0 / 100	11 ms	4344 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], dp[MAXN+10][MAXN+10], ans;

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

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

int main()
{
    int i, j, k;
    for(i=1; i<=MAXN; i++) inv[i]=pow(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()-1;

    for(i=0; i<S; i++) dp[0][i]=1;
    for(i=1; i<=N; i++)
    {
        dp[i][0]=dp[i-1][S-1];
        for(j=getcomp(A[i]); j<getcomp(B[i]); j++)
        {
            ll bino=1;
            ll sz=comp[j+1]-comp[j];
            for(k=1; k<=i; k++)
            {
                if(k>sz) break;
                bino=bino*(sz-k+1)%MOD;
                bino=bino*inv[k]%MOD;
                dp[i][j]+=dp[i-k][j-1]*bino%MOD; dp[i][j]%=MOD;
            }
        }
        for(j=1; j<S; j++) dp[i][j]+=dp[i][j-1], dp[i][j]%=MOD;
    }
    ans=dp[N][S-1]-1;
    if(ans<0) ans+=MOD;
    printf("%lld", ans);
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:31:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &N);
     ~~~~~^~~~~~~~~~
boat.cpp:34:14: 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