add abc405c.rs

rchaser53 · rchaser53 · commit 2908e2bb5fe7 · 2025-05-18T21:39:30.000+09:00
diff --git a/src/abc/abc405c.rs b/src/abc/abc405c.rs
@@ -0,0 +1,27 @@
+/** THIS IS AN OUTPUT FILE. NOT EDIT THIS FILE DIRECTLY. **/
+use proconio::input;
+use proconio::marker::*;
+use std::marker::PhantomData;
+use std::cmp::*;
+use std::collections::*;
+use itertools::Itertools;
+
+
+fn main() {
+  input! {
+    n:usize,
+    a:[usize;n]
+  }
+
+  let mut memo = vec![0;n+1];
+  for i in (0..n).rev() {
+    memo[i] = memo[i+1] + a[i];
+  }
+
+  let mut result = 0usize;
+  for i in 0..n-1 {
+    result += memo[i+1] * a[i];
+  }
+
+  println!("{}", result);
+}
