[UVa] 543 - Goldbache's Conjecture

#include <cstdio>
#include <iostream>
#include <cstring>
#include <vector>
#include <cmath>
using namespace std;
#define PMAX 1000010
bool ver[PMAX];
vector<int> plist;
int sieve(int lim) {
  int i, j, k;
  plist.clear();
  plist.push_back(2);
  for (int i=3 ; i<=lim ; i+=2) {
    if (ver[i]==false) {
      plist.push_back(i);
      for (int j=3 ; i*j<=lim ; j+=2) {
        ver[i*j] = true;
      }
    }
  }
}

int main() {
  sieve(PMAX);
  int n;

  while (scanf("%d",&n)==1) {
    if (n == 0) break; // Program terminated
    int a=-1, b=-1;
    bool found = false;
    for (int i=0 ; i<plist.size() && plist[i]<=n ; i++) {
      a = n-plist[i];
      b = plist[i];
      if (a>1 && b>1 && (a&1) && (b&1) && ver[a] == false && ver[b] == false) {
        found = true;
        break;
      }
    }
    if (found == true) {
      printf("%d = %d + %d\n",n,b,a); 
    } else {
      printf("Goldbach's conjecture is wrong.\n");
    }

  }
  return 0;
}