Merge pull request #113 from jxs/missing-number

Added Rust missing-number solution

Author: mre

Diff for: problems/missing-number/missing-number.rs

@@ -0,0 +1,33 @@
+//returns the missing number, or in the case Vec is empty, returns None
+fn missing_number(input: &[usize]) -> Option<usize> {
+    if input.is_empty() {
+        return None;
+    }
+
+    let non_missing: usize = (1..input.len() + 2).sum();
+    let missing: usize = input.iter().sum();
+
+    Some(non_missing - missing)
+}
+
+fn main() {
+    println!(
+        "missing number: {}",
+        missing_number(&[1, 2, 3, 4, 6]).unwrap()
+    );
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn returns_none_if_vec_is_empty() {
+        assert_eq!(None, missing_number(&[]));
+    }
+
+    #[test]
+    fn finds_missing_number_sequential_range() {
+        assert_eq!(4, missing_number(&[1, 2, 3, 5, 6]).unwrap());
+    }
+}