Update sol12.dart

project_euler/problem_12/sol12.dart

@@ -1,54 +1,54 @@
 import 'dart:math';
 
+List<int> prime_sieve(int limit) {
+ int sieve_bound = (limit - 1) ~/ 2;
+ int upper_sqrt = (sqrt(limit).toInt() - 1) ~/ 2;
+ List<bool> prime_bits = List.generate(sieve_bound + 1, (_) => true);
 
-List<int> prime_sieve(int limit){
- int sieve_bound = (limit - 1) ~/ 2;
- int upper_sqrt = (sqrt(limit).toInt() - 1) ~/ 2;
- List<bool> prime_bits = List.generate(sieve_bound + 1, (_) => true);
+ for (int i = 1; i <= upper_sqrt; ++i)
+ if (prime_bits[i])
+ for (int j = i * (i + 1) * 2; j <= sieve_bound; j += 2 * i + 1)
+ prime_bits[j] = false;
 
- for(int i = 1 ; i <= upper_sqrt ; ++i) 
- if (prime_bits[i])
- for(int j = i * (i + 1) * 2 ; j <= sieve_bound ; j += 2 * i + 1)
- prime_bits[j] = false;
+ List<int> primes = [2];
+ for (int i = 1; i <= sieve_bound; ++i)
+ if (prime_bits[i]) primes.add(2 * i + 1);
 
- List<int> primes = [2];
- for(int i = 1 ; i <= sieve_bound ; ++i)
- if (prime_bits[i])
- primes.add(2 * i + 1);
-
- return primes;
+ return primes;
 }
 
-int prime_factorisation_number_of_divisors(int n, List<int> primes){
- int nod = 1;
- int remain = n;
- for(int i = 0 ; i < primes.length ; ++i){
- if (primes[i] * primes[i] > n)
- return nod * 2;
- int power = 1;
- while (remain % primes[i] == 0){
- power += 1;
- remain ~/= primes[i];
- }
- nod *= power;
- if (remain == 1) break;
- }
- return nod;
+int prime_factorisation_number_of_divisors(int n, List<int> primes) {
+ int nod = 1;
+ int remain = n;
+ for (int i = 0; i < primes.length; ++i) {
+ if (primes[i] * primes[i] > n) return nod * 2;
+ int power = 1;
+ while (remain % primes[i] == 0) {
+ power += 1;
+ remain ~/= primes[i];
+ }
+ nod *= power;
+ if (remain == 1) break;
+ }
+ return nod;
 }
 
-
 void main() {
- int i = 2;
- int count = 0;
- int odd = 2;
- int even = 2;
- List<int> primes = prime_sieve(500);
- while (count < 500){
- even = i % 2 == 0 ? prime_factorisation_number_of_divisors(i + 1, primes) : even;
- odd = i % 2 != 0 ? prime_factorisation_number_of_divisors((i + 1) ~/ 2, primes) : odd;
- count = even * odd;
- ++i;
- }
- int ans = (i * (i - 1) * 0.5).toInt();
- print("First Triangle Number with more than 500 divisors: $ans");
+ int i = 2;
+ int count = 0;
+ int odd = 2;
+ int even = 2;
+ List<int> primes = prime_sieve(500);
+ while (count < 500) {
+ even = i % 2 == 0
+ ? prime_factorisation_number_of_divisors(i + 1, primes)
+ : even;
+ odd = i % 2 != 0
+ ? prime_factorisation_number_of_divisors((i + 1) ~/ 2, primes)
+ : odd;
+ count = even * odd;
+ ++i;
+ }
+ int ans = (i * (i - 1) * 0.5).toInt();
+ print("First Triangle Number with more than 500 divisors: $ans");
 }