219 solved. (#55)

Author: zwfang

README.md

@@ -27,6 +27,7 @@ continually updating 😃.
 * [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`*
+* [219. Contains Duplicate II](src/0219_contains_duplicate_2/contains_duplicate_2.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)

src/0219_contains_duplicate_2/contains_duplicate_2.go

@@ -0,0 +1,27 @@
+/*
+219. Contains Duplicate II
+https://leetcode.com/problems/contains-duplicate-ii/
+
+Given an array of integers and an integer k,
+find out whether there are two distinct indices i and j in the array
+such that nums[i] = nums[j] and the absolute difference between i and j is at most k.
+*/
+// time: 2019-01-07
+
+package cond
+
+// using hash table
+// time complexity: O(n)
+// space complexity: O(n)
+func containsNearbyDuplicate(nums []int, k int) bool {
+	record := make(map[int]int, len(nums))
+	for i, v := range nums {
+		if j, ok := record[v]; ok {
+			if i-j <= k {
+				return true
+			}
+		}
+		record[v] = i
+	}
+	return false
+}

src/0219_contains_duplicate_2/contains_duplicate_2_test.go

@@ -0,0 +1,19 @@
+package cond
+
+import "testing"
+
+func TestContainsNearbyDuplicate(t *testing.T) {
+	testCases := [][]int{
+		{1, 2, 3, 1},
+		{1, 0, 1, 1},
+		{1, 2, 3, 1, 2, 3},
+	}
+	ks := []int{3, 1, 2}
+	expected := []bool{true, true, false}
+
+	for index, nums := range testCases {
+		if res := containsNearbyDuplicate(nums, ks[index]); res != expected[index] {
+			t.Errorf("expected %t, got %t", expected[index], res)
+		}
+	}
+}

src/README.md

@@ -69,6 +69,7 @@
 |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`*|
+|0219|[219. Contains Duplicate II](0219_contains_duplicate_2/contains_duplicate_2.go)|Easy|*`map`*|
 |0226|[Invert Binary Tree](./0226_invert_binary_tree/invert_binary_tree.go)|Easy|*`recursion; `* *`binary tree`*|
 |0283|[Move Zeroes(solution1)](./0283_move_zeroes/move_zeroes.go) <br/>  [Move Zeroes(solution2)](./0283_move_zeroes/move_zeroes2.go)|Easy|*`array`*|
 |0300|[Longest Increasing Subsequence](./0300_longest_increasing_subsequence/lis.go)|Medium|*`dp`*|