Submission #448068

#	Time	Username	Problem	Language	Result	Execution time	Memory
448068		urd05	Boat (APIO16_boat)	C++17	100 / 100	496 ms	332 KiB

boat

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

vector<int> press;
int n;
typedef pair<int,int> P;
P arr[501];
long long psum[501];
long long save[501];
const int mod=1e9+7;
long long value[501];

long long fastpow(long long a,long long b) {
    if (b==0) {
        return 1;
    }
    if (b%2==1) {
        return (fastpow(a,b-1)*a)%mod;
    }
    long long half=fastpow(a,b/2);
    return (half*half)%mod;
}

int main(void) {
    scanf("%d",&n);
    press.push_back(1);
    for(int i=1;i<=n;i++) {
        int a,b;
        scanf("%d %d",&a,&b);
        arr[i]=P(a,b);
        press.push_back(a);
        press.push_back(b+1);
    }
    sort(press.begin(),press.end());
    press.erase(unique(press.begin(),press.end()),press.end());
    for(int i=1;i<=n;i++) {
        arr[i].first=lower_bound(press.begin(),press.end(),arr[i].first)-press.begin()+1;
        arr[i].second=lower_bound(press.begin(),press.end(),arr[i].second+1)-press.begin();
    }
    for(int i=0;i<n;i++) {
        psum[i]=1;
    }
    for(int i=1;i<press.size();i++) {
        int sz=press[i]-press[i-1];
        value[0]=sz;
        for(int j=1;j<=n;j++) {
            value[j]=(value[j-1]*(sz+j))%mod;
            value[j]*=fastpow(j+1,mod-2);
            value[j]%=mod;
        }
        vector<long long> v;
        save[0]=0;
        for(int j=1;j<=n;j++) {
            if (arr[j].first<=i&&i<=arr[j].second) {
                v.insert(v.begin(),psum[j-1]);
            }
            save[j]=0;
            for(int k=0;k<v.size();k++) {
                save[j]+=(value[k]*v[k])%mod;
                save[j]%=mod;
            }
        }
        for(int j=0;j<=n;j++) {
            //printf("%lld ",save[j]);
            psum[j]+=save[j];
            psum[j]%=mod;
        }
        //printf("\n");
    }
    printf("%lld",psum[n]);
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:43:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   43 |     for(int i=1;i<press.size();i++) {
      |                 ~^~~~~~~~~~~~~
boat.cpp:58:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   58 |             for(int k=0;k<v.size();k++) {
      |                         ~^~~~~~~~~
boat.cpp:25:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   25 |     scanf("%d",&n);
      |     ~~~~~^~~~~~~~~
boat.cpp:29:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   29 |         scanf("%d %d",&a,&b);
      |         ~~~~~^~~~~~~~~~~~~~~

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