ALDS1_1_C | Prime Numbers

Calendar Clock iconCalendar Clock icon

AOJ

Table of contents

# Problem

http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_1_C

# Explanation

Fast prime numbers finding algorithm

# Time complexity

# Solution

// C++ 14
#include <iostream>
#include <string>
#include <vector>
#include <list>
#include <algorithm>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <unordered_map>
#include <math.h>

#define ll long long
#define Int int
#define loop(x, start, end) for(Int x = start; x < end; x++)
#define loopdown(x, start, end) for(int x = start; x > end; x--)
#define rep(n) for(int x = 0; x < n; x++)
#define span(a,x,y) a.begin()+x,a.begin()+y
#define span_all(a) a.begin(),a.end()
#define len(x) (x.size())
#define last(x) (*(x.end()-1))

using namespace std;
#define MAX_N 10001
Int N;
vector<Int> ns(MAX_N, -1);

bool isPrime(Int x) {
  if (x == 1) return false;
  if (x == 2) return true;
  if (x % 2 == 0) return false;
  
  Int sqrtX = Int(sqrt(x));
  for (Int n = 3; n <= sqrtX; n += 2)  if (x % n == 0) return false;
  return true;
}

void input() {
  cin >> N;
  loop(n,0,N) cin >> ns[n];
  ns.resize(N);
}

void solve() {
  Int count = 0;
  loop(n,0,N) count += isPrime(ns[n]);
  cout << count << endl;
}

int main() {
  input();
  solve();
  return 0;
}

Shun

Github Circle icon

Remote freelancer. A web and mobile application enginner.
Traveling around the world based on East Asia.
I'm looking forward to your job offers from all over the world!

Offer jobs or contact me!

Comments