Data commit

Task/Prime-triangle/Rust/prime-triangle.rust

@@ -0,0 +1,71 @@
+fn is_prime(n: u32) -> bool {
+    assert!(n < 64);
+    ((1u64 << n) & 0x28208a20a08a28ac) != 0
+}
+
+fn prime_triangle_row(a: &mut [u32]) -> bool {
+    if a.len() == 2 {
+        return is_prime(a[0] + a[1]);
+    }
+    for i in (1..a.len() - 1).step_by(2) {
+        if is_prime(a[0] + a[i]) {
+            a.swap(i, 1);
+            if prime_triangle_row(&mut a[1..]) {
+                return true;
+            }
+            a.swap(i, 1);
+        }
+    }
+    false
+}
+
+fn prime_triangle_count(a: &mut [u32]) -> u32 {
+    let mut count = 0;
+    if a.len() == 2 {
+        if is_prime(a[0] + a[1]) {
+            count += 1;
+        }
+    } else {
+        for i in (1..a.len() - 1).step_by(2) {
+            if is_prime(a[0] + a[i]) {
+                a.swap(i, 1);
+                count += prime_triangle_count(&mut a[1..]);
+                a.swap(i, 1);
+            }
+        }
+    }
+    count
+}
+
+fn print(a: &[u32]) {
+    if a.is_empty() {
+        return;
+    }
+    print!("{:2}", a[0]);
+    for x in &a[1..] {
+        print!(" {:2}", x);
+    }
+    println!();
+}
+
+fn main() {
+    use std::time::Instant;
+    let start = Instant::now();
+    for n in 2..21 {
+        let mut a: Vec<u32> = (1..=n).collect();
+        if prime_triangle_row(&mut a) {
+            print(&a);
+        }
+    }
+    println!();
+    for n in 2..21 {
+        let mut a: Vec<u32> = (1..=n).collect();
+        if n > 2 {
+            print!(" ");
+        }
+        print!("{}", prime_triangle_count(&mut a));
+    }
+    println!();
+    let time = start.elapsed();
+    println!("\nElapsed time: {} milliseconds", time.as_millis());
+}