Data commit

Task/Calkin-Wilf-sequence/Rust/calkin-wilf-sequence.rust

@@ -0,0 +1,54 @@
+// [dependencies]
+// num = "0.3"
+
+use num::rational::Rational;
+
+fn calkin_wilf_next(term: &Rational) -> Rational {
+    Rational::from_integer(1) / (Rational::from_integer(2) * term.floor() + 1 - term)
+}
+
+fn continued_fraction(r: &Rational) -> Vec<isize> {
+    let mut a = *r.numer();
+    let mut b = *r.denom();
+    let mut result = Vec::new();
+    loop {
+        let (q, r) = num::integer::div_rem(a, b);
+        result.push(q);
+        a = b;
+        b = r;
+        if a == 1 {
+            break;
+        }
+    }
+    let len = result.len();
+    if len != 0 && len % 2 == 0 {
+        result[len - 1] -= 1;
+        result.push(1);
+    }
+    result
+}
+
+fn term_number(r: &Rational) -> usize {
+    let mut result: usize = 0;
+    let mut d: usize = 1;
+    let mut p: usize = 0;
+    for n in continued_fraction(r) {
+        for _ in 0..n {
+            result |= d << p;
+            p += 1;
+        }
+        d ^= 1;
+    }
+    result
+}
+
+fn main() {
+    println!("First 20 terms of the Calkin-Wilf sequence are:");
+    let mut term = Rational::from_integer(1);
+    for i in 1..=20 {
+        println!("{:2}: {}", i, term);
+        term = calkin_wilf_next(&term);
+    }
+    let r = Rational::new(83116, 51639);
+    println!("{} is the {}th term of the sequence.", r, term_number(&r));
+}