Add implementation for leetcode problems from mock interview.

leetcode_118.py

@@ -0,0 +1,45 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+"""
+Created on Sun Feb 22 14:16:29 2026
+
+@author: rishigoswamy
+
+    LeetCode 118: Pascal's Triangle
+    Link: https://leetcode.com/problems/pascals-triangle/
+
+    Approach:
+    Build the triangle row by row.
+
+    Observations:
+        - First and last elements of every row are 1.
+        - For any middle element:
+              triangle[i][j] = triangle[i-1][j-1] + triangle[i-1][j]
+
+    Steps:
+        1. Iterate from row 0 to numRows-1.
+        2. Initialize each row with all 1s.
+        3. Fill middle values using previous row.
+        4. Append row to result.
+
+    // Time Complexity : O(n^2)
+        Total elements generated ≈ n(n+1)/2.
+    // Space Complexity : O(n^2)
+        Output storage for triangle.
+"""
+
+from typing import List
+
+class Solution:
+    def generate(self, numRows: int) -> List[List[int]]:
+        res = []
+
+        for i in range(0, numRows):
+            temp = [1] * (i+1)
+
+            for j in range(1, i):
+                temp[j] = res[i-1][j-1] + res[i-1][j]
+
+            res.append(temp)
+
+        return res

leetcode_532.py

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+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+"""
+Created on Sun Feb 22 14:18:19 2026
+
+@author: rishigoswamy
+
+    LeetCode 532: K-diff Pairs in an Array
+    Link: https://leetcode.com/problems/k-diff-pairs-in-an-array/
+
+    Approach:
+    Use a frequency hashmap.
+
+    Case 1: k == 0
+        We are looking for numbers that appear more than once.
+        Each number with frequency > 1 contributes exactly one pair.
+
+    Case 2: k > 0
+        For each unique number x,
+        check whether (x + k) exists in the map.
+
+    Important:
+        We use unique keys to avoid duplicate pair counting.
+
+    // Time Complexity : O(n)
+        Build hashmap in O(n)
+        Iterate unique keys in O(n)
+    // Space Complexity : O(n)
+        Hashmap storage
+"""
+
+from typing import List
+from collections import defaultdict
+
+class Solution:
+    def findPairs(self, nums: List[int], k: int) -> int:
+        hMap = defaultdict(int)
+        for num in nums:
+            hMap[num] += 1
+
+        count = 0
+        if k == 0:
+            for key in hMap:
+                if hMap[key] > 1:
+                    count+=1
+            return count
+
+        for key in hMap:
+            if k + key in hMap:
+                count+=1
+
+        return count