Data update

Task/Permutations-Derangements/Rust/permutations-derangements.rs

@@ -0,0 +1,56 @@
+fn deranged(depth: usize, len: usize, d: &mut Vec<u8>, show: bool) -> i128 {
+    let mut count: i128 = 0;
+
+    if depth == len {
+        if show {
+            for i in 0..len {
+                print!("{}", (d[i] + 'a' as u8) as char);
+            }
+            println!();
+        }
+        return 1_i128;
+    }
+    for i in (depth..len).rev() {
+        if i != d[depth].into() {
+            let mut tmp = d[i];
+            d[i] = d[depth];
+            d[depth] = tmp;
+            count += deranged(depth + 1, len, d, show);
+            tmp = d[i];
+            d[i] = d[depth];
+            d[depth] = tmp;
+        }
+    }
+    return count;
+}
+
+fn gen_n(n: usize, show: bool) -> i128 {
+    let a = &mut [0_u8; 1024].to_vec();
+    for i in 0..n {
+        a[i] = i as u8;
+    }
+    return deranged(0, n, a, show);
+}
+
+fn sub_fact(n: usize) -> i128 {
+    return if n < 2 {
+        (1 - n) as i128
+    } else {
+        (sub_fact(n - 1) + sub_fact(n - 2)) * ((n - 1) as i128)
+    };
+}
+
+fn main() {
+    println!("Deranged Four:");
+    gen_n(4, true);
+
+    println!("\nCompare list vs calc:");
+    for i in 0..10 {
+        println!("{}:\t{}\t{}", i, gen_n(i, false), sub_fact(i));
+    }
+
+    println!("\nfurther calc:");
+    for i in 10..33 {
+        println!("{}: {}", i, sub_fact(i));
+    }
+}