Submission #975453

#	Time	Username	Problem	Language	Result	Execution time	Memory
975453		Kenjikrab	Boat (APIO16_boat)	C++14	9 / 100	1683 ms	8664 KiB

boat

#include<bits/stdc++.h>
#define int long long
#define pii pair<int,int>
#define fi first
#define se second
using namespace std;
int const mod=1e9+7;
map<int,int> ind;
vector<int> val;
vector<int> fen(1010,0);
void upd(int idx,int val)
{
    idx+=2;
    for(int i=idx;i<1010;i+=i&-i)fen[i]+=val,fen[i]%=mod;
}
int qr(int idx)
{
    idx+=2;
    int ret=0;
    for(int i=idx;i>0;i-=i&-i)ret+=fen[i],ret%=mod;
    return ret;
}

// int pow(int a,int b)
// {
//     if(b==0)return 1;
//     if(b==1)return a;
//     int ret=pow(a,b/2);
//     if(b%2==0)return (ret*ret)%mod;
//     else return (((ret*ret)%mod)*a)%mod;
// }
// map<int,int> inverse;
// int inv(int a)
// {
//     if(inverse[a]!=0)return inverse[a];
//     inverse[a]=pow(a,mod-2);
//     return inverse[a];
// }

// int choose(int a,int b)
// {
//     if(b>a)return 0;
//     int ret=1;
//     for(int i=b+1;i<=a;i++)
//     {
//         ret*=i;
//         ret%=mod;
//     }
//     for(int i=2;i<=a-b;i++)
//     {
//         ret*=inv(i);
//         ret%=mod;
//     }
//     return ret;
// }

int choose(int n, int r)
{
    if(r>n)return 0;
    // p holds the value of n*(n-1)*(n-2)...,
    // k holds the value of r*(r-1)...
    int p = 1, k = 1;
 
    // C(n, r) == C(n, n-r),
    // choosing the smaller value
    if (n - r < r)
        r = n - r;
 
    if (r != 0) {
        while (r) {
            p *= n;
            k *= r;
 
            // gcd of p, k
            int m = __gcd(p, k);
 
            // dividing by gcd, to simplify
            // product division by their gcd 
            // saves from the overflow
            p /= m;
            k /= m;
 
            n--;
            r--;
        }
 
        // k should be simplified to 1
        // as C(n, r) is a natural number
        // (denominator should be 1 ) .
    }
 
    else
        p = 1;
    return p;
}
signed main()
{
    int n;
    cin>>n;
    vector<pii> info;
    set<int> temp;
    for(int i=0;i<n;i++)
    {
        int a,b;
        cin>>a>>b;
        temp.insert(a);
        temp.insert(b+1);
        info.push_back({a,b+1});
    }
    for(auto it:temp)
    {
        val.push_back(it);
        ind[it]=val.size()-1;
    }
    vector<vector<int>> pre(510,vector<int>(1010,-2));
    vector<int> latest(1010,-1);
    upd(-1,1);
    vector<vector<int>> dp(510,vector<int>(1010,0));
    for(int i=0;i<n;i++)
    {
        //cout<<endl<<i<<":";
        for(int j=ind[info[i].se]-1;j>=ind[info[i].fi];j--)
        {
            //cout<<j<<" ";
            
            int bef=latest[j];
            pre[i][j]=latest[j];
            latest[j]=i;
            int a=qr(j),b=(val[j+1]-val[j]),c=0;
            dp[i][j]=a;
            int ans=a*b;
            ans%=mod;
            int k=2;
            //cout<<i<<" "<<j<<" "<<ans<<" ";
            while(bef!=-1)
            {
                ans+=dp[bef][j]*choose(b+k-2,k);
                ans%=mod;
                bef=pre[bef][j];
                k++;
                //cout<<endl<<bef<<" "<<ans<<" ";
            }
           // cout<<endl;
            upd(j+1,ans);
        }
    }
    cout<<(qr(1007)+mod-1)%mod;
    return 0;
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:129:45: warning: unused variable 'c' [-Wunused-variable]
  129 |             int a=qr(j),b=(val[j+1]-val[j]),c=0;
      |                                             ^

• Subtask 1: 9 / 9
• Subtask 2: 0 / 22
• Subtask 3: 0 / 27
• Subtask 4: 0 / 42