diff --git a/README.md b/README.md
index 702625f..138f4fe 100644
--- a/README.md
+++ b/README.md
@@ -26,6 +26,7 @@ continually updating 😃.
 * [200. Number of Islands](src/0200_number_of_island/number_of_island.go)  *`dfs;`* *`bfs`*
 * [209. Minimum Size Subarray Sum](./src/0209_minimum_size_subarray_sum/minimum_size_subarray_sum.go)  *`sliding window`*
 * [215. Kth Largest Element in an Array](./src/0215_kth_largest_element_in_an_array/kthleiaa.go)  *`sort`*
+* [217. Contains Duplicate](src/0217_contains_duplicate/contains_duplicate.go)  *`map`*
 * [283. Move Zeroes(solution1)](./src/0283_move_zeroes/move_zeroes.go)  *`sliding window`*
 * [283. Move Zeroes(solution2)](./src/0283_move_zeroes/move_zeroes2.go)  *`sliding window`*
 * [303. Range Sum Query - Immutable](src/0303_range_sum_query/rsqim.go)
diff --git a/src/0217_contains_duplicate/contains_duplicate.go b/src/0217_contains_duplicate/contains_duplicate.go
new file mode 100644
index 0000000..dd032a6
--- /dev/null
+++ b/src/0217_contains_duplicate/contains_duplicate.go
@@ -0,0 +1,28 @@
+/*
+217. Contains Duplicate
+https://leetcode.com/problems/contains-duplicate/
+
+Given an array of integers, find if the array contains any duplicates.
+
+Your function should return true if any value appears at least twice in the array,
+and it should return false if every element is distinct.
+*/
+// time: 2019年01月07日
+
+package cd
+
+// using HashTable
+// time complexity: O(n)
+// space complexity: O(n)
+func containsDuplicate(nums []int) bool {
+	record := make(map[int]int)
+
+	for _, num := range nums {
+		if _, ok := record[num]; !ok {
+			record[num] = 1
+		} else {
+			return true
+		}
+	}
+	return false
+}
diff --git a/src/0217_contains_duplicate/contains_duplicate_test.go b/src/0217_contains_duplicate/contains_duplicate_test.go
new file mode 100644
index 0000000..b82a1a8
--- /dev/null
+++ b/src/0217_contains_duplicate/contains_duplicate_test.go
@@ -0,0 +1,17 @@
+package cd
+
+import "testing"
+
+func TestContainsDuplicate(t *testing.T) {
+	testCases := [][]int{
+		{1, 2, 3, 1},
+		{1, 2, 3, 4},
+	}
+	expected := []bool{true, false}
+
+	for index, nums := range testCases {
+		if res := containsDuplicate(nums); res != expected[index] {
+			t.Errorf("expected %t, got %t", expected[index], res)
+		}
+	}
+}
diff --git a/src/README.md b/src/README.md
index 729a8d4..fac16ad 100644
--- a/src/README.md
+++ b/src/README.md
@@ -68,6 +68,7 @@
 |0206|[206. Reverse Linked List](0206_reverse_linked_list/reverse_linked_list.go)|Easy|*`linked list`*|
 |0209|[Minimum Size Subarray Sum](./0209_minimum_size_subarray_sum/minimum_size_subarray_sum.go)|Medium|*`sliding window`*|
 |0215|[215. Kth Largest Element in an Array](0215_kth_largest_element_in_an_array/kthleiaa.go)|Medium|*`sort`*|
+|0217|[217. Contains Duplicate](0217_contains_duplicate/contains_duplicate.go)|Easy|*`map`*|
 |0226|[Invert Binary Tree](./0226_invert_binary_tree/invert_binary_tree.go)|Easy|*`recursion; `* *`binary tree`*|
 &#124;0283&#124;[Move Zeroes(solution1)](./0283_move_zeroes/move_zeroes.go) <br/> [Move Zeroes(solution2)](./0283_move_zeroes/move_zeroes2.go)&#124;Easy&#124;*`array`*&#124;
 &#124;0300&#124;[Longest Increasing Subsequence](./0300_longest_increasing_subsequence/lis.go)&#124;Medium&#124;*`dp`*&#124;
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