Data commit

Task/Hofstadter-Q-sequence/Rust/hofstadter-q-sequence.rust

@@ -0,0 +1,26 @@
+fn hofq(q: &mut Vec<u32>, x : u32) -> u32 {
+    let cur_len=q.len()-1;
+    let i=x as usize;
+    if i>cur_len {
+        // extend storage
+        q.reserve(i+1);
+        for j in (cur_len+1)..(i+1) {
+            let qj=(q[j-q[j-1] as usize]+q[j-q[j-2] as usize]) as u32;
+            q.push(qj);
+        }
+    }
+    q[i]
+}
+
+fn main() {
+    let mut q_memo: Vec<u32>=vec![0,1,1];
+    let mut q=|i| {hofq(&mut q_memo, i)};
+    for i in 1..11 {
+        println!("Q({})={}", i, q(i));
+    }
+    println!("Q(1000)={}", q(1000));
+    let q100001=q(100_000); // precompute all
+    println!("Q(100000)={}", q100000);
+    let nless=(1..100_000).fold(0,|s,i|{if q(i+1)<q(i) {s+1} else {s}});
+    println!("Term is less than preceding term {} times", nless);
+}