Solve #268

Author: aylei

src/lib.rs

@@ -210,3 +210,4 @@ mod n0258_add_digits;
 mod n0260_single_number_iii;
 mod n0263_ugly_number;
 mod n0264_ugly_number_ii;
+mod n0268_missing_number;

src/n0268_missing_number.rs

@@ -0,0 +1,43 @@
+/**
+ * [268] Missing Number
+ *
+ * Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.
+ *
+ * Example 1:
+ *
+ *
+ * Input: [3,0,1]
+ * Output: 2
+ *
+ *
+ * Example 2:
+ *
+ *
+ * Input: [9,6,4,2,3,5,7,0,1]
+ * Output: 8
+ *
+ *
+ * Note:<br />
+ * Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity?
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn missing_number(nums: Vec<i32>) -> i32 {
+        ((nums.len() + 1)  * nums.len()) as i32 / 2 - nums.into_iter().fold(0, |acc, v| { acc + v })
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_268() {
+        assert_eq!(Solution::missing_number(vec![3,0,1]), 2);
+    }
+}