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Assignment 2 #92

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bff7f13
Complete a mock coding interview assignment
Feb 2, 2026
120b1c3
Complete Assignment 2: Practice Interview - Implement is_duplicate, a…
Feb 8, 2026
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173 changes: 149 additions & 24 deletions 02_activities/assignments/assignment_1.ipynb
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Original file line number Diff line number Diff line change
Expand Up @@ -25,17 +25,25 @@
},
{
"cell_type": "code",
"execution_count": null,
"execution_count": 2,
"metadata": {},
"outputs": [],
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"1\n"
]
}
],
"source": [
"import hashlib\n",
"\n",
"def hash_to_range(input_string: str) -> int:\n",
" hash_object = hashlib.sha256(input_string.encode())\n",
" hash_int = int(hash_object.hexdigest(), 16)\n",
" return (hash_int % 3) + 1\n",
"input_string = \"your_first_name_here\"\n",
"input_string = \"anika\"\n",
"result = hash_to_range(input_string)\n",
"print(result)\n"
]
Expand Down Expand Up @@ -67,7 +75,7 @@
},
{
"cell_type": "code",
"execution_count": null,
"execution_count": 3,
"metadata": {},
"outputs": [],
"source": [
Expand Down Expand Up @@ -112,7 +120,7 @@
},
{
"cell_type": "code",
"execution_count": 1,
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
Expand Down Expand Up @@ -165,11 +173,23 @@
},
{
"cell_type": "code",
"execution_count": null,
"execution_count": 14,
"metadata": {},
"outputs": [],
"outputs": [
{
"data": {
"text/plain": [
"\" Find the first integer in a list that repeats. 'First' means the duplicate that appears first in the list when reading left to right. Return the duplicate value. If no duplicates, return -1. \""
]
},
"execution_count": 14,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"# Your answer here"
"# Your answer here\n",
"\" Find the first integer in a list that repeats. 'First' means the duplicate that appears first in the list when reading left to right. Return the duplicate value. If no duplicates, return -1. \""
]
},
{
Expand All @@ -181,11 +201,37 @@
},
{
"cell_type": "code",
"execution_count": null,
"execution_count": 21,
"metadata": {},
"outputs": [],
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Example 1:\n",
"Input: nums = [2, 3, 3, 2]\n",
"Output: 3\n",
"Explanation: 3 appears twice at indices 1 and 2. 2 appears later (index 3).\n",
"\n",
"Example 2:\n",
"Input: nums = [1, 2, 3, 4, 5]\n",
"Output: -1\n",
"Explanation: No duplicates.\n"
]
}
],
"source": [
"# Your answer here"
"# Your answer here\n",
"\n",
"print(\"Example 1:\")\n",
"print(\"Input: nums = [2, 3, 3, 2]\")\n",
"print(\"Output: 3\")\n",
"print(\"Explanation: 3 appears twice at indices 1 and 2. 2 appears later (index 3).\")\n",
"print()\n",
"print(\"Example 2:\")\n",
"print(\"Input: nums = [1, 2, 3, 4, 5]\")\n",
"print(\"Output: -1\")\n",
"print(\"Explanation: No duplicates.\")"
]
},
{
Expand All @@ -198,11 +244,20 @@
},
{
"cell_type": "code",
"execution_count": null,
"execution_count": 22,
"metadata": {},
"outputs": [],
"source": [
"# Your answer here"
"# Your answer here\n",
"from typing import List\n",
"\n",
"def first_duplicate(nums: List[int]) -> int:\n",
" seen = set()\n",
" for num in nums:\n",
" if num in seen:\n",
" return num\n",
" seen.add(num)\n",
" return -1"
]
},
{
Expand All @@ -215,11 +270,38 @@
},
{
"cell_type": "code",
"execution_count": null,
"execution_count": 24,
"metadata": {},
"outputs": [],
"outputs": [
{
"data": {
"text/plain": [
"\" We track seen numbers in a set. Iterate through the list. If the current number is already in the set, it's the first duplicate → return it. Otherwise, add it to the set. If loop finishes, no duplicates → return -1.\\n\\nExample walkthrough: nums = [3, 1, 4, 2, 5, 1, 6]\\n\\nnum = 3, not in set(), add → {3}\\n\\nnum = 1, not in {3}, add → {3, 1}\\n\\nnum = 4, not in {3, 1}, add → {3, 1, 4}\\n\\nnum = 2, not in {3, 1, 4}, add → {3, 1, 4, 2}\\n\\nnum = 5, not in {3, 1, 4, 2}, add → {3, 1, 4, 2, 5}\\n\\nnum = 1, found in set → return 1\\n\""
]
},
"execution_count": 24,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"# Your answer here"
"# Your answer here\n",
"\"\"\" We track seen numbers in a set. Iterate through the list. If the current number is already in the set, it's the first duplicate → return it. Otherwise, add it to the set. If loop finishes, no duplicates → return -1.\n",
"\n",
"Example walkthrough: nums = [3, 1, 4, 2, 5, 1, 6]\n",
"\n",
"num = 3, not in set(), add → {3}\n",
"\n",
"num = 1, not in {3}, add → {3, 1}\n",
"\n",
"num = 4, not in {3, 1}, add → {3, 1, 4}\n",
"\n",
"num = 2, not in {3, 1, 4}, add → {3, 1, 4, 2}\n",
"\n",
"num = 5, not in {3, 1, 4, 2}, add → {3, 1, 4, 2, 5}\n",
"\n",
"num = 1, found in set → return 1\n",
"\"\"\""
]
},
{
Expand All @@ -232,11 +314,35 @@
},
{
"cell_type": "code",
"execution_count": null,
"execution_count": 29,
"metadata": {},
"outputs": [],
"outputs": [
{
"data": {
"text/plain": [
"'\\nTime complexity: O(n) - single pass through list, set operations O(1) average.\\nn = length of input list nums.\\nWe loop through list once: for num in nums: → O(n) iterations.\\nEach iteration: check if num in seen: (O(1) for set lookup) and seen.add(num) (O(1) )\\nTotal: O(n) × O(1) = O(n)\\n\\nSpace complexity: O(n) - in worst case store all elements in set.\\nseen = set() stores unique elements.\\nWorst case: no duplicates, store all n elements → O(n) space.\\nBest case: duplicate at beginning → store only 1 element → O(1) space.\\nWe report worst case: O(n).\\n'"
]
},
"execution_count": 29,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"# Your answer here"
"# Your answer here\n",
"\"\"\"\n",
"Time complexity: O(n) - single pass through list, set operations O(1) average.\n",
"n = length of input list nums.\n",
"We loop through list once: for num in nums: → O(n) iterations.\n",
"Each iteration: check if num in seen: (O(1) for set lookup) and seen.add(num) (O(1) )\n",
"Total: O(n) × O(1) = O(n)\n",
"\n",
"Space complexity: O(n) - in worst case store all elements in set.\n",
"seen = set() stores unique elements.\n",
"Worst case: no duplicates, store all n elements → O(n) space.\n",
"Best case: duplicate at beginning → store only 1 element → O(1) space.\n",
"We report worst case: O(n).\n",
"\"\"\""
]
},
{
Expand All @@ -249,11 +355,30 @@
},
{
"cell_type": "code",
"execution_count": null,
"execution_count": 28,
"metadata": {},
"outputs": [],
"outputs": [
{
"data": {
"text/plain": [
"\" \\nUse two nested loops. For each element, check if it appears again later in the list. Return the first one found.\\n\\nHow it works:\\n-Outer loop picks each element (index i).\\n-Inner loop checks all elements after it (index j).\\n-If match found, it's the first duplicate (because we check left to right).\\n\""
]
},
"execution_count": 28,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"# Your answer here"
"# Your answer here\n",
"\"\"\" \n",
"Use two nested loops. For each element, check if it appears again later in the list. Return the first one found.\n",
"\n",
"How it works:\n",
"-Outer loop picks each element (index i).\n",
"-Inner loop checks all elements after it (index j).\n",
"-If match found, it's the first duplicate (because we check left to right).\n",
"\"\"\""
]
},
{
Expand Down Expand Up @@ -301,7 +426,7 @@
],
"metadata": {
"kernelspec": {
"display_name": "Python 3 (ipykernel)",
"display_name": "algos-env",
"language": "python",
"name": "python3"
},
Expand All @@ -315,7 +440,7 @@
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython3",
"version": "3.11.5"
"version": "3.11.3"
}
},
"nbformat": 4,
Expand Down
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