From 558e768380991a222c77ff72416c629ab922a91a Mon Sep 17 00:00:00 2001
From: ashish-badhe <badhe.a@northeastern.edu>
Date: Mon, 20 Oct 2025 10:31:20 -0400
Subject: [PATCH 1/3] K-diff pairs

---
 KDiffPairs.java | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 KDiffPairs.java

diff --git a/KDiffPairs.java b/KDiffPairs.java
new file mode 100644
index 00000000..fecaf4f2
--- /dev/null
+++ b/KDiffPairs.java
@@ -0,0 +1,38 @@
+
+// 532. K-diff Pairs in an Array
+// https://leetcode.com/problems/k-diff-pairs-in-an-array/description/
+
+/**
+ * Time Complexity: O(n) since we iterate over each element
+ * Space Complexity: O(n) since in worst case we store all elements
+ */
+
+class Solution {
+    public int findPairs(int[] nums, int k) {
+        Map<Integer, Integer> map = new HashMap<>();
+
+        int count = 0;
+
+        for(int num : nums){ // count frequency of numbers
+            map.put(num, map.getOrDefault(num, 0) + 1);
+        }
+
+        for(int num : map.keySet()){ // iterating on keys as we want unique pairs
+
+            int anotherNumber = num + k;
+
+            // if k is 0, we need to check if the same number exists more than once as we cannot consider same number
+            if(k == 0){ 
+               if(map.get(anotherNumber) > 1){ 
+                    count++;
+               }
+            }else{
+               if(map.containsKey(anotherNumber)){
+                    count++;
+               }                
+            }
+        }
+
+        return count;
+    }
+}
\ No newline at end of file

From 042ae461f272af9763405fd5985b516fc85e4f30 Mon Sep 17 00:00:00 2001
From: ashish-badhe <badhe.a@northeastern.edu>
Date: Mon, 20 Oct 2025 11:17:54 -0400
Subject: [PATCH 2/3] Pascals Triangle

---
 PascalsTriangle.java | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 PascalsTriangle.java

diff --git a/PascalsTriangle.java b/PascalsTriangle.java
new file mode 100644
index 00000000..c14a0230
--- /dev/null
+++ b/PascalsTriangle.java
@@ -0,0 +1,37 @@
+// 118. Pascal's Triangle
+// https://leetcode.com/problems/pascals-triangle/description/
+
+/**
+ * Time Complexity: O(n * m) ~ O(n^2) since we iterate over each element
+ * Space Complexity: O(1) since no auxillary space as we dont consider result 
+ */
+
+
+
+class Solution {
+    public List<List<Integer>> generate(int numRows) {
+        List<List<Integer>> result = new ArrayList<>();
+
+        for(int i = 2 ; i < numRows ; i++){
+
+            List<Integer> currList = new ArrayList<>();
+
+            for(int j = 0 ; j <= i ; j++){
+
+                if(j == 0 || j == i){ // if first or last index , fill with 1
+                    currList.add(1);
+                }else{
+                    List<Integer> prevList = result.get(i - 1);
+
+                    int currNumber = prevList.get(j - 1) + prevList.get(j); // else add previous list elements
+
+                    currList.add(currNumber);
+                }
+            }
+
+            result.add(currList);
+        }
+
+        return result;
+    }
+}
\ No newline at end of file

From 56fad37921e9174c39ba3ccb728228f4f54480ee Mon Sep 17 00:00:00 2001
From: ashish-badhe <badhe.a@northeastern.edu>
Date: Mon, 20 Oct 2025 12:11:38 -0400
Subject: [PATCH 3/3] fixed logic to start from first row

---
 PascalsTriangle.java | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/PascalsTriangle.java b/PascalsTriangle.java
index c14a0230..489b9dbf 100644
--- a/PascalsTriangle.java
+++ b/PascalsTriangle.java
@@ -12,18 +12,18 @@ class Solution {
     public List<List<Integer>> generate(int numRows) {
         List<List<Integer>> result = new ArrayList<>();
 
-        for(int i = 2 ; i < numRows ; i++){
+        for(int i = 0 ; i < numRows ; i++){
 
             List<Integer> currList = new ArrayList<>();
 
             for(int j = 0 ; j <= i ; j++){
 
-                if(j == 0 || j == i){ // if first or last index , fill with 1
+                if(j == 0 || j == i){
                     currList.add(1);
                 }else{
                     List<Integer> prevList = result.get(i - 1);
 
-                    int currNumber = prevList.get(j - 1) + prevList.get(j); // else add previous list elements
+                    int currNumber = prevList.get(j - 1) + prevList.get(j);
 
                     currList.add(currNumber);
                 }