diff --git a/source/lib.rs b/source/lib.rs
index 7dd3558..d1b3fad 100644
--- a/source/lib.rs
+++ b/source/lib.rs
@@ -14,6 +14,7 @@ pub mod palindrome_number;
 pub mod plus_one;
 pub mod reverse_integer;
 pub mod roman_to_integer;
+pub mod set_mismatch;
 pub mod two_sum;
 pub mod valid_anagram;
 pub mod valid_palindrome;
diff --git a/source/set_mismatch/mod.rs b/source/set_mismatch/mod.rs
new file mode 100644
index 0000000..880db08
--- /dev/null
+++ b/source/set_mismatch/mod.rs
@@ -0,0 +1,31 @@
+pub fn find_error_nums(numbers: Vec<i32>) -> Vec<i32> {
+  // Uncomment FromIterator in Leetcode since they're using Rust Edition 2018.
+  // Edition 2021 has this trait in its prelude.
+
+  // use std::iter::FromIterator;
+  use std::collections::HashSet;
+
+  let range = 1..=numbers.len() as i32;
+  let mut numbers_set = HashSet::<_>::new();
+
+  let mut duplicate = 0;
+
+  for number in numbers {
+    if numbers_set.insert(number) {
+      continue;
+    }
+
+    duplicate = number;
+  }
+
+  let mut missing = 0;
+
+  for number in range {
+    if !numbers_set.contains(&number) {
+      missing = number;
+      break;
+    }
+  }
+
+  vec![duplicate, missing]
+}
diff --git a/tests/set_mismatch.rs b/tests/set_mismatch.rs
new file mode 100644
index 0000000..326eccb
--- /dev/null
+++ b/tests/set_mismatch.rs
@@ -0,0 +1,12 @@
+use leetcode::set_mismatch::find_error_nums;
+
+use test_case::test_case;
+
+#[test_case(&[1, 2, 2, 4], &[2, 3]; "example 1")]
+#[test_case(&[1, 1], &[1, 2]; "example 2")]
+#[test_case(&[2, 2], &[2, 1]; "edge 1")]
+#[test_case(&[3, 2, 3, 4, 6, 5], &[3, 1]; "edge 2")]
+#[test_case(&[3, 2, 2], &[2, 1]; "edge 3")]
+fn test_set_mismatch(input: &[i32], expected: &[i32]) {
+  assert_eq!(find_error_nums(input.to_vec()), expected);
+}