Submission #823871

#	Time	Username	Problem	Language	Result	Execution time	Memory
823871		Sandarach151	Lutrija (COCI19_lutrija)	C++17	0 / 70	1 ms	320 KiB

lutrija

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

long long M;
long long qexp (long long b, long long e) { //quick exponentiation (see below)
    if (e == 0) return 1;
    if (e == 1) return b%M;
    long long h = qexp(b, e/2);
    h *= h;
    h %= M;
    if (e%2 == 0) return h;
    return (h*b)%M;
}
bool isPrime(long long N) {
    if (N <= 1) return 0;
    if (N <= 3) return 1;
    if (N == 4) return 0;
    long long s = (N-1)&(1-N), d = (N-1)/s;
    M = N;
    for (long long i = 0, K = 30; i < K; ++i) {
        long long witness = rand()%(N-4) + 2;  //generate random witness between [2, N-2]
        long long a = qexp(witness, d);
        if (a == 1 || a == N-1) continue;
        bool pass = 1;
        for (long long k = 1; k < s && pass; k<<=1) {
            a*=a;
            a%=N;
            if (a == N-1) pass = false;
        }
        if (pass) return 0; /* not a prime due to witness */
    }
    return 1;
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    long long a, b;
    vector<long long> vect;
    cin >> a >> b;
    bool swapped = false;
    if(a==2){
        swap(a, b);
        swapped = true;
    }
    long long tempa = a;
    bool res1 = true;
    while(!isPrime(abs(b-a))){
        a+=2;
        if(!isPrime(a)){
            res1 = false;
            break;
        }
    }
    a = tempa;
    bool res2 = true;
    while(!isPrime(abs(b-a))){
        a-=2;
        if(!isPrime(a)){
            res2 = false;
            break;
        }
    }
    if(!res1 && !res2){
        cout << -1 << '\n';
    }
    else{
		if(res1){
			a = tempa;
			vect.push_back(a);
			while(!isPrime(abs(b-a))){
				a+=2;
				vect.push_back(a);
			}
			vect.push_back(b);
		}
		else{
			a = tempa;
			vect.push_back(a);
			while(!isPrime(abs(b-a))){
				a-=2;
				vect.push_back(a);
			}
			vect.push_back(b);
		}
		if(!swapped){
			cout << vect.size() << '\n';
			for(long long i=0; i<vect.size(); i++){
				cout << vect[i] << ' ';
			}
		}
		else{
			cout << vect.size() << '\n';
			for(long long i=vect.size()-1; i>=0; i--){
				cout << vect[i] << ' ';
			}
		}
	}
    return 0;
}

Compilation message (stderr)

lutrija.cpp: In function 'int main()':
lutrija.cpp:88:24: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   88 |    for(long long i=0; i<vect.size(); i++){
      |                       ~^~~~~~~~~~~~

• Subtask 1: 0 / 7
• Subtask 2: 0 / 7
• Subtask 3: 0 / 7
• Subtask 4: 0 / 7
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• Subtask 10: 0 / 7