Data commit

Task/Kolakoski-sequence/Rust/kolakoski-sequence.rust

@@ -0,0 +1,60 @@
+use itertools::Itertools;
+
+fn get_kolakoski_sequence(iseq: &[usize], size: &usize) -> Vec<usize> {
+    assert!(*size > 0);
+    assert!(!iseq.is_empty());
+
+    let mut kseq: Vec<usize> = Vec::default();
+
+    // create an itertor which keeps repeating the initial sequence infinitely
+    let repeater = iseq.iter().cloned().cycle();
+
+    // push the very first element, repeated as many times as the number
+    kseq.extend_from_slice(&vec![*iseq.get(0).unwrap()].repeat(*iseq.get(0).unwrap()));
+
+    //start cycling throught the initial sequence, but skip the very first one
+    for (k_counter, elem) in repeater.enumerate().skip(1) {
+        // push the given element
+        kseq.push(elem);
+
+        // and repeat the current element as many times
+        // as it's needed based on the previous elements
+        kseq.extend_from_slice(&vec![elem].repeat(*kseq.get(k_counter).unwrap() - 1));
+
+        // finish generation when the Kolakoski sequence has reached the given length
+        if kseq.len() >= *size {
+            break;
+        }
+    }
+
+    // truncate it as it might have more elements than needed
+    kseq[0..*size].to_vec()
+}
+
+fn is_kolakoski(kseq: &[usize]) -> bool {
+    assert!(!kseq.is_empty());
+
+    // calculate the RLE
+    let rle: Vec<usize> = kseq
+        .iter()
+        .batching(|it| {
+            it.next()
+                .map(|v| it.take_while_ref(|&v2| v2 == v).count() + 1)
+        })
+        .collect();
+
+    rle.iter().zip(kseq).filter(|&(a, b)| a == b).count() == rle.len()
+}
+
+fn main() {
+    let lengths = vec![20, 20, 30, 30];
+    let seqs = vec![vec![1, 2], vec![2, 1], vec![1, 3, 1, 2], vec![1, 3, 2, 1]];
+
+    for (seq, length) in seqs.iter().zip(&lengths) {
+        let kseq = get_kolakoski_sequence(&seq, length);
+
+        println!("Starting sequence: {:?}", seq);
+        println!("Kolakoski sequence: {:?}", kseq);
+        println!("Possible Kolakoski sequence? {:?}", is_kolakoski(&kseq));
+    }
+}