June 2018 Update

Task/Semiprime/Rust/semiprime.rust

@@ -0,0 +1,56 @@
+extern crate primal;
+
+fn isqrt(n: usize) -> usize {
+    (n as f64).sqrt() as usize
+}
+
+fn is_semiprime(mut n: usize) -> bool {
+    let root = isqrt(n) + 1;
+    let primes1 = primal::Sieve::new(root);
+    let mut count = 0;
+
+    for i in primes1.primes_from(2).take_while(|&x| x < root) {
+        while n % i == 0 {
+            n /= i;
+            count += 1;
+        }
+        if n == 1 {
+            break;
+        }
+    }
+
+    if n != 1 {
+        count += 1;
+    }
+    count == 2
+}
+
+#[test]
+fn test1() {
+    assert_eq!((2..10).filter(|&n| is_semiprime(n)).count(), 3);
+}
+
+#[test]
+fn test2() {
+    assert_eq!((2..100).filter(|&n| is_semiprime(n)).count(), 34);
+}
+
+#[test]
+fn test3() {
+    assert_eq!((2..1_000).filter(|&n| is_semiprime(n)).count(), 299);
+}
+
+#[test]
+fn test4() {
+    assert_eq!((2..10_000).filter(|&n| is_semiprime(n)).count(), 2_625);
+}
+
+#[test]
+fn test5() {
+    assert_eq!((2..100_000).filter(|&n| is_semiprime(n)).count(), 23_378);
+}
+
+#[test]
+fn test6() {
+    assert_eq!((2..1_000_000).filter(|&n| is_semiprime(n)).count(), 210_035);
+}