A few problems

missing-number/sol.rs

@@ -0,0 +1,8 @@
+impl Solution {
+    pub fn missing_number(nums: Vec<i32>) -> i32 {
+        let expected_sum = (nums.len() * (nums.len() + 1) / 2) as i32;
+        nums
+            .iter()
+            .fold(expected_sum, |acc, x| acc - *x)
+    }
+}