Scala で Project Euler Problem 10
Problem 7 を 流用
scala> var prime_list = List(3) prime_list: List[Int] = List(3) scala> var num = 5 num: Int = 5 scala> scala> while (num < 2000000) { | var num_sqrt = Math.sqrt(num) | var fPrime = true | scala.util.control.Breaks.breakable { | prime_list.foreach { p => | if (p > num_sqrt) { | scala.util.control.Breaks.break | } else if (num % p == 0) { | fPrime = false | scala.util.control.Breaks.break | } | } | } | | if (fPrime) { | prime_list = prime_list:::List(num) | } | num += 2 | } warning: there were 1 deprecation warnings; re-run with -deprecation for details scala> prime_list.last res6: Int = 1999993 scala> prime_list = 2::prime_list prime_list: List[Int] = List(2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 94... scala> prime_list.sum res7: Int = 1179908154
いやになるほど遅いので、素直に奇数で試し割り
scala> var prime_sum = 2 + 3 prime_sum: Int = 5 scala> var num = 5 num: Int = 5 scala> while (num < 2000000) { | var num_sqrt = Math.sqrt(num) | var odd_num = 3 | var fPrime = true | var fWhile = true | while (fWhile) { | if (odd_num > num_sqrt) { | fWhile = false | } else if (num % odd_num == 0) { | fWhile = false | fPrime = false | } else odd_num += 2 | } | if (fPrime) { | prime_sum += num | } | num += 2 | } warning: there were 1 deprecation warnings; re-run with -deprecation for details scala> prime_sum res3: Int = 1179908154
incorrect って言われちゃったよ...
もしかして桁あふれ?
scala> var prime_sum = 2L + 3L prime_sum: Long = 5 scala> var num = 5L num: Long = 5 scala> while (num < 2000000L) { | var num_sqrt = Math.sqrt(num) | var odd_num = 3L | var fPrime = true | var fWhile = true | while (fWhile) { | if (odd_num > num_sqrt) { | fWhile = false | } else if (num % odd_num == 0) { | fWhile = false | fPrime = false | } else odd_num += 2 | } | if (fPrime) { | prime_sum += num | } | num += 2 | } warning: there were 1 deprecation warnings; re-run with -deprecation for details scala> prime_sum res5: Long = 142913828922