day 102: add negatives tolerant solution

day102/problem.go

@@ -41,3 +41,26 @@ func ContiguousSumNonNegative(nums []int, k int) []int {
 	}
 	return result
 }
+
+// ContiguousSumNegatives returns the
+// contiguous subset that sums to K.
+// This implementation tolerates negative values.
+// Runtime is O(N) and O(N) space.
+func ContiguousSumNegatives(nums []int, k int) []int {
+	var result []int
+	var sum int
+	m := make(map[int]int)
+	for i := range nums {
+		sum += nums[i]
+		if sum-k == 0 {
+			result = nums[0 : i+1]
+			break
+		}
+		if start, found := m[sum-k]; found {
+			result = nums[start+1 : i+1]
+			break
+		}
+		m[sum] = i
+	}
+	return result
+}

day102/problem_test.go

@@ -85,3 +85,28 @@ func BenchmarkContiguousSumNonNegative(b *testing.B) {
 		}
 	}
 }
+
+func TestContiguousSumNegatives(t *testing.T) {
+	t.Parallel()
+	for _, tc := range nonNegativeTestcases {
+		if result := ContiguousSumNegatives(tc.input, tc.k); !reflect.DeepEqual(tc.expected, result) {
+			t.Errorf("Expected %v got %v", tc.expected, result)
+		}
+	}
+	for _, tc := range negativeTestcases {
+		if result := ContiguousSumNegatives(tc.input, tc.k); !reflect.DeepEqual(tc.expected, result) {
+			t.Errorf("Expected %v got %v", tc.expected, result)
+		}
+	}
+}
+
+func BenchmarkContiguousSumNegatives(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range nonNegativeTestcases {
+			ContiguousSumNegatives(tc.input, tc.k)
+		}
+		for _, tc := range negativeTestcases {
+			ContiguousSumNegatives(tc.input, tc.k)
+		}
+	}
+}