A few problems

contains-duplicate/sol.rs

@@ -0,0 +1,8 @@
+use std::collections::HashSet;
+
+impl Solution {
+    pub fn contains_duplicate(nums: Vec<i32>) -> bool {
+        let mut exists = HashSet::new();
+        !nums.into_iter().all(|n| exists.insert(n))
+    }
+}