Algorithm/ProjectEuler/47.cpp at master · feelpython/Algorithm · GitHub

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#include <iostream>
#include <sstream>
#include <algorithm>
#include <iterator>
#include <vector>
#include <set>
#include <cmath>
using namespace std;

#define REP(i,n) for(int i=0;i<(n);++i)
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
typedef long long LL;

vector<string> split( const string& s, const string& delim =" " ) {
  vector<string> res;
  string t;
  for ( int i = 0 ; i != s.size() ; i++ ) {
    if ( delim.find( s[i] ) != string::npos ) {
      if ( !t.empty() ) {
	res.push_back( t );
	t = "";
      }
    } else {
      t += s[i];
    }
  }
  if (!t.empty() ) {
    res.push_back(t);
  }
  return res;
}

int s2i(string s) {
  stringstream ss;
  ss << s;
  int res;
  ss >> res;
  return res;
}

string i2s(int n) {
  stringstream ss;
  ss << n;
  string res;
  ss >> res;
  return res;
}

int plist[10000],pcount=0;
int mm[50000];

int prime(int n){
  int i;
  if ((n!=2&&!(n%2))||(n!=3&&!(n%3))||(n!=5&&!(n%5))||(n!=7&&!(n%7)))
    return 0;
  for (i=0;plist[i]*plist[i]<=n;i++)
    if (!(n%plist[i]))
      return 0;
  return n>1;
}

void initprime(){
  int i;
  mm[2] = 1;
  for (plist[pcount++]=2,i=3;i<50000;i++)
    if (prime(i)) {
      mm[i] = 1;
      plist[pcount++]=i;
    }
}

bool isok(int n) {
  //cout << "n = " << n << endl;
  int res = 0;
  REP(i,pcount) {
    if (n % plist[i] == 0) {
      ++res;
      if (res > 4) return false;
      while (n % plist[i] == 0) n /= plist[i];
    }
    if (plist[i] * plist[i] > n) {
      ++res;
      break;
    }
  }
  //cout << res << endl;
  return res == 4;
}

void run() {
  initprime();
  vector<int> mm;
  for (int i = 647; ; ++i) {
    if (isok(i)) {
      mm.push_back(i);
      cout << "size = " << mm.size() << endl;
      if (mm.size() == 4) {
	cout << mm[0] << endl;
	return;
      }
    } else {
      mm.clear();
    }
  }
}

int main() {
  run();
}