Contains duplicate II

Author: volodimyr

219.contains_diplicate_ii/contains.go

@@ -0,0 +1,43 @@
+// 219. Contains duplicate II
+// Topics: 'Array', 'Hash Table', 'Sliding Window'
+
+// Given an integer array nums and an integer k, return true if there are two distinct indices i and j in the array such that nums[i] == nums[j] and abs(i - j) <= k.
+
+// Example 1:
+
+// Input: nums = [1,2,3,1], k = 3
+// Output: true
+
+// Example 2:
+
+// Input: nums = [1,0,1,1], k = 1
+// Output: true
+
+// Example 3:
+
+// Input: nums = [1,2,3,1,2,3], k = 2
+// Output: false
+
+// Constraints:
+
+// 1 <= nums.length <= 105
+// -109 <= nums[i] <= 109
+// 0 <= k <= 105
+
+package containsdiplicateii
+
+func containsNearbyDuplicate(nums []int, k int) bool {
+	m := map[int]struct{}{}
+	L := 0
+	for R := range len(nums) {
+		if R-L > k {
+			delete(m, nums[L])
+			L += 1
+		}
+		if _, ok := m[nums[R]]; ok {
+			return true
+		}
+		m[nums[R]] = struct{}{}
+	}
+	return false
+}

219.contains_diplicate_ii/contains_test.go

@@ -0,0 +1,71 @@
+package containsdiplicateii
+
+import "testing"
+
+func TestContainsNearbyDuplicate(t *testing.T) {
+	tests := []struct {
+		name string
+		nums []int
+		k    int
+		want bool
+	}{
+		{
+			name: "Example 1",
+			nums: []int{1, 2, 3, 1},
+			k:    3,
+			want: true,
+		},
+		{
+			name: "Example 2",
+			nums: []int{1, 0, 1, 1},
+			k:    1,
+			want: true,
+		},
+		{
+			name: "Example 3",
+			nums: []int{1, 2, 3, 1, 2, 3},
+			k:    2,
+			want: false,
+		},
+		{
+			name: "No duplicates",
+			nums: []int{1, 2, 3, 4, 5},
+			k:    3,
+			want: false,
+		},
+		{
+			name: "Duplicate but too far apart",
+			nums: []int{1, 2, 1},
+			k:    1,
+			want: false,
+		},
+		{
+			name: "Single element",
+			nums: []int{99},
+			k:    10,
+			want: false,
+		},
+		{
+			name: "k is zero",
+			nums: []int{1, 1},
+			k:    0,
+			want: false,
+		},
+		{
+			name: "Large k covers whole array",
+			nums: []int{5, 6, 7, 5},
+			k:    10,
+			want: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := containsNearbyDuplicate(tt.nums, tt.k)
+			if got != tt.want {
+				t.Errorf("containsNearbyDuplicate(%v, %d) = %v; want %v",
+					tt.nums, tt.k, got, tt.want)
+			}
+		})
+	}
+}