complete 30160.rs 33913.rs

storage/zeta/rs/completed/33913.rs

@@ -0,0 +1,37 @@
+use std::io::stdin;
+
+const MOD: usize = 1_000_000_007;
+
+fn main() {
+    let mut line = String::new();
+    stdin().read_line(&mut line).unwrap();
+
+    let n = line.trim().parse::<usize>().unwrap();
+
+    /*
+        f[0] even =  1 // empty
+        f[0] odd  =  0
+        f[1] even = 24 // without SC
+        f[1] odd  =  2 // with SC
+
+        f[2] even = f[1] even * 24 + f[1] odd * 2
+        f[2] odd  = f[1] even * 2  + f[1] odd * 24 
+
+    */
+
+    let mut f0e = 1;
+    let mut f0i = 0;
+    let mut f1e = 24;
+    let mut f1i = 2;
+
+    for _ in 2..=n {
+        let f2e = (f1e * 24 + f1i * 2) % MOD;
+        let f2i = (f1e * 2 + f1i * 24) % MOD;
+        f0e = f1e;
+        f0i = f1i;
+        f1e = f2e;
+        f1i = f2i;
+    }
+
+    println!("{}", f1e);
+}