diff --git a/docs/hackerrank/interview_preparation_kit/miscellaneous/ctci-big-o.md b/docs/hackerrank/interview_preparation_kit/miscellaneous/ctci-big-o.md
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+# [Time Complexity: Primality](https://www.hackerrank.com/challenges/ctci-big-o)
+
+- Difficulty:  `#medium`
+- Category: `#ProblemSolvingBasic`
+
+## Using bitwise operations
+
+A prime is a natural number greater than `1` that has no positive divisors other
+than `1` and itself.
+Given `p` integers, determine the primality of each integer and return `Prime`
+or `Not prime` on a new line.
+
+**Note**: If possible, try to come up with an $ \mathcal{O}(\sqrt{n}) $
+primality algorithm, or see what sort of optimizations you can come up with for
+san $ \mathcal{O}(\sqrt{n}) $ algorithm. Be sure to check out the Editorial
+after submitting your code.
+
+## Function Description
+
+Complete the primality function in the editor below.
+primality has the following parameter(s):
+
+- `int` n: an integer to test for primality
+
+## Returns
+
+- string: Prime if  is prime, or Not prime
+
+## Input Format
+
+The first line contains an integer, , the number of integers to check for primality.
+Each of the  subsequent lines contains an integer, , the number to test.
+
+## Constraints
+
+- $ 1 \leq p \leq 30 $
+- $ 1 \leq n \leq 2 × 10^9 $
+
+## Sample Input
+
+```text
+STDIN   Function
+-----   --------
+3       p = 3 (number of values to follow)
+12      n = 12 (first number to check)
+5       n = 5
+7       n = 7
+```
+
+## Sample Output
+
+```text
+Not prime
+Prime
+Prime
+```
+
+## Explanation
+
+We check the following $ p = 3 $ integers for primality:
+
+1. $ n = 12 $ is divisible by numbers other than $ 1 $ and itself
+  (i.e.: $ 2 $, $ 3 $, $ 4 $, $ 6 $).
+1. $ n = 5 $ is only divisible  and itself.
+1. $ n = 7 $ is only divisible  and itself.
diff --git a/exercises/hackerrank/interview_preparation_kit/miscellaneous/ctci_big_o.go b/exercises/hackerrank/interview_preparation_kit/miscellaneous/ctci_big_o.go
new file mode 100644
index 0000000..6a8fd92
--- /dev/null
+++ b/exercises/hackerrank/interview_preparation_kit/miscellaneous/ctci_big_o.go
@@ -0,0 +1,48 @@
+/**
+ * @link Problem definition [[docs/hackerrank/interview_preparation_kit/miscellaneous/ctci-big-o.md]] # noqa
+ */
+
+package hackerrank
+
+import "math"
+
+const NOT_PRIME = "Not prime"
+const PRIME = "Prime"
+
+func primeFactor(n int32) *int32 {
+	if n < 2 {
+		return nil
+	}
+
+	divisor := n
+	var maxPrimeFactor *int32 = nil
+
+	var i int32 = 2
+	for i <= int32(math.Sqrt(float64(divisor))) {
+		if divisor%i == 0 {
+			divisor = int32(divisor / i)
+			maxPrimeFactor = &divisor
+		} else {
+			i += 1
+		}
+	}
+	if maxPrimeFactor == nil {
+		val := int32(n)
+		return &val
+	}
+
+	return maxPrimeFactor
+}
+
+func primality(n int32) string {
+	pf := primeFactor(n)
+	if pf == nil || *pf != n {
+		return NOT_PRIME
+	}
+
+	return PRIME
+}
+
+func Primality(n int32) string {
+	return primality(n)
+}
diff --git a/exercises/hackerrank/interview_preparation_kit/miscellaneous/ctci_big_o.testcases.json b/exercises/hackerrank/interview_preparation_kit/miscellaneous/ctci_big_o.testcases.json
new file mode 100644
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--- /dev/null
+++ b/exercises/hackerrank/interview_preparation_kit/miscellaneous/ctci_big_o.testcases.json
@@ -0,0 +1,66 @@
+[
+  {
+    "title": "Sample Test case 0",
+    "tests": [
+      {
+        "input": 12,
+        "answer": "Not prime"
+      },
+      {
+        "input": 5,
+        "answer": "Prime"
+      },
+      {
+        "input": 7,
+        "answer": "Prime"
+      }
+    ]
+  },
+  {
+    "title": "Sample Test case 1",
+    "tests": [
+      {
+        "input": 31,
+        "answer": "Prime"
+      },
+      {
+        "input": 33,
+        "answer": "Not prime"
+      }
+    ]
+  },
+  {
+    "title": "Sample Test case 2",
+    "tests": [
+      {
+        "input": 2,
+        "answer": "Prime"
+      },
+      {
+        "input": 7,
+        "answer": "Prime"
+      },
+      {
+        "input": 1982,
+        "answer": "Not prime"
+      },
+      {
+        "input": 14582734,
+        "answer": "Not prime"
+      },
+      {
+        "input": 9891,
+        "answer": "Not prime"
+      }
+    ]
+  },
+  {
+    "title": "Sample Test case 0",
+    "tests": [
+      {
+        "input": 1,
+        "answer": "Not prime"
+      }
+    ]
+  }
+]
diff --git a/exercises/hackerrank/interview_preparation_kit/miscellaneous/ctci_big_o_test.go b/exercises/hackerrank/interview_preparation_kit/miscellaneous/ctci_big_o_test.go
new file mode 100644
index 0000000..0f19f14
--- /dev/null
+++ b/exercises/hackerrank/interview_preparation_kit/miscellaneous/ctci_big_o_test.go
@@ -0,0 +1,50 @@
+package hackerrank
+
+import (
+	"fmt"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"gon.cl/algorithms/utils"
+)
+
+type TimeComplexityPrimalityTest struct {
+	Input    int32  `json:"input"`
+	Expected string `json:"answer"`
+}
+
+type TimeComplexityPrimalityTests struct {
+	Title string                        `json:"title"`
+	Tests []TimeComplexityPrimalityTest `json:"tests"`
+}
+
+var TimeComplexityPrimalityTestCases []TimeComplexityPrimalityTests
+
+// You can use testing.T, if you want to test the code without benchmarking
+func TimeComplexityPrimalitySetupSuite(t testing.TB) {
+	wd, _ := os.Getwd()
+	filepath := wd + "/ctci_big_o.testcases.json"
+	t.Log("Setup test cases from JSON: ", filepath)
+
+	var _, err = utils.LoadJSON(filepath, &TimeComplexityPrimalityTestCases)
+	if err != nil {
+		t.Log(err)
+	}
+}
+
+func TestTimeComplexityPrimality(t *testing.T) {
+
+	TimeComplexityPrimalitySetupSuite(t)
+
+	for _, tt := range TimeComplexityPrimalityTestCases {
+		for _, testCase := range tt.Tests {
+			testname := fmt.Sprintf("Primality(%d) => %s \n", testCase.Input, testCase.Expected)
+
+			t.Run(testname, func(t *testing.T) {
+				ans := Primality(testCase.Input)
+				assert.Equal(t, testCase.Expected, ans)
+			})
+		}
+	}
+}