Solve contains-duplicate-ii.

source/contains_duplicate_ii/mod.rs

@@ -0,0 +1,15 @@
+pub fn contains_nearby_duplicate(numbers: Vec<i32>, range: i32) -> bool {
+  // Uncomment FromIterator in Leetcode since they're using Rust Edition 2018.
+  // Edition 2021 has this trait in its prelude.
+
+  // use std::iter::FromIterator;
+  fn contains_duplicate(numbers: &[i32]) -> bool {
+    std::collections::HashSet::<_>::from_iter(numbers).len() != numbers.len()
+  }
+
+  contains_duplicate(&numbers)
+    && numbers
+      .as_slice()
+      .windows(std::cmp::min((range + 1) as usize, numbers.len()))
+      .any(contains_duplicate)
+}

source/lib.rs

@@ -1,5 +1,6 @@
 pub mod add_binary;
 pub mod contains_duplicate;
+pub mod contains_duplicate_ii;
 pub mod excel_sheet_column_number;
 pub mod excel_sheet_column_title;
 pub mod implement_strstr;

tests/contains_duplicate_ii.rs

@@ -0,0 +1,12 @@
+use leetcode::contains_duplicate_ii::contains_nearby_duplicate;
+
+use test_case::test_case;
+
+#[test_case(&[1, 2, 3, 1], 3, true; "example 1")]
+#[test_case(&[1, 0, 1, 1], 1, true; "example 2")]
+#[test_case(&[1, 2, 3, 1, 2, 3], 2, false; "example 3")]
+#[test_case(&[99, 99], 2, true; "range higher than numbers")]
+#[test_case(&(-25000..=30000).collect::<Vec<i32>>(), 35000, false; "massive input")]
+fn test_contains_duplicate_ii(numbers: &[i32], range: i32, expected: bool) {
+  assert_eq!(contains_nearby_duplicate(numbers.to_vec(), range), expected);
+}