complete 4674.rs 9912.rs 10826.rs 12140.rs 14452.rs 17021.rs 17386.rs 20929.rs

storage/zeta/rs/completed/9912.rs

@@ -0,0 +1,53 @@
+use std::io::{read_to_string, stdin};
+
+fn fact(x: usize) -> usize {
+    static F: [usize; 16] = [
+        1,
+        1,
+        2,
+        6,
+        24,
+        120,
+        720,
+        5040,
+        40320,
+        362880,
+        3628800,
+        39916800,
+        479001600,
+        6227020800,
+        87178291200,
+        1307674368000,
+    ];
+    F[x]
+}
+
+fn main() {
+    let temp = read_to_string(stdin()).unwrap();
+    let mut iter = temp
+        .split_ascii_whitespace()
+        .map(|x| x.parse::<usize>().unwrap());
+
+    let n = iter.next().unwrap();
+    let perm = (0..n).map(|_| iter.next().unwrap()).collect::<Vec<usize>>();
+
+    let mut vis = vec![false; n];
+
+    let mut res = 0;
+
+    for i in 0..n {
+        let k = perm[i];
+        let r = n - i - 1;
+        let mut cnt = 0;
+        for j in 0..k {
+            if !vis[j] {
+                cnt += 1;
+            }
+        }
+        res += fact(r) * cnt;
+        // cl
+        vis[k] = true;
+    }
+
+    println!("{}", res + 1);
+}