diff --git a/leetcode/645.py b/leetcode/645.py
new file mode 100644
index 0000000..54641ba
--- /dev/null
+++ b/leetcode/645.py
@@ -0,0 +1,26 @@
+from typing import List
+
+
+class Solution:
+
+    def findErrorNums(self, nums: List[int]) -> List[int]:
+        sumSetNums = sum(set(nums))
+        sumNums = sum(nums)
+        return [sumNums - sumSetNums, ((len(nums) * (len(nums) + 1)) // 2) - sumSetNums]
+
+    def findErrorNums1(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        return_list = [0, 0]
+        for i in range(1, n + 1):
+            if i not in nums:
+                return_list[1] = i
+                break
+
+        for i in range(1, n + 1):
+            if i in nums:
+                nums.remove(i)
+                if i in nums:
+                    return_list[0] = i
+                    break
+
+        return return_list