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  1. var BitArray = function(size) {
  2.   this.length = size;
  3.   this.buffer = new ArrayBuffer(Math.ceil(this.length / 32) * 4);
  4.   this.words  = new Uint32Array(this.buffer);
  5. };
  6.  
  7. BitArray.prototype.size = function() {
  8.   return this.length;
  9. };
  10.  
  11. BitArray.prototype.set = function(bitIndex) {
  12.   var wordIndex = Math.floor(bitIndex / 32);
  13.   this.words[wordIndex] |= (1 << bitIndex);
  14. };
  15.  
  16. BitArray.prototype.get = function(bitIndex) {
  17.   var wordIndex  = Math.floor(bitIndex / 32);
  18.   return !!(this.words[wordIndex] & (1 << bitIndex));
  19. };
  20.  
  21. function maxPalindromicPrime(bound) {
  22.   var sieve_size = (bound - 1) % 6 < 4 ? Math.floor(bound / 6) * 2 + 1 : Math.floor((bound + 1) / 3);
  23.   var sieve = new BitArray(sieve_size);
  24.   var limit = Math.floor(Math.sqrt(bound));
  25.   for(var i = 1;; ++i) {
  26.     if(!sieve.get(i)) {
  27.       var p = i * 3 + (i & 1) + 1;
  28.       if(p > limit) break;
  29.       for(var j = p * 2 + i; j < sieve_size; j += p * 2)
  30.         sieve.set(j);
  31.       for(var j = p * 2 - i - 1; j < sieve_size; j += p * 2)
  32.         sieve.set(j);
  33.     }
  34.   }
  35.  
  36.   for(var i = sieve_size - 1; i > 0; --i) {
  37.     if(!sieve.get(i)) {
  38.       var n = i * 3 + (i & 1) + 1;
  39.       if(isPalindrome(n)) {
  40.         return n;
  41.       }
  42.     }
  43.   }
  44. }
  45.  
  46. function isPalindrome(n) {
  47.   var s = n.toString();
  48.   var len = s.length;
  49.   for(var i = 0; i < len / 2; ++i) {
  50.     if(s[i] != s[len - i - 1]) return false;
  51.   }
  52.   return true;
  53. }
  54.  
  55. console.log(maxPalindromicPrime(Math.pow(2, 30)));
Runtime error #stdin #stdout #stderr 4.99s 76352KB
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/spoj/nodejs_run: line 2: 28950 CPU time limit exceeded node prog.js
https://ideone.com/hCN7CJ
language:
Node.js (node 11.12.0)
created:
10 years ago
visibility:
public

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