v1

k-diff-pairs.py

@@ -0,0 +1,15 @@
+# O(n) time, O(n) space
+class Solution:
+    def findPairs(self, nums: List[int], k: int) -> int:
+        # {1: 2, 3: 1, 4: 1, 5: 1}
+        # k=2
+        # nums = [3,1,4,1,5]
+        counter = Counter(nums)
+        pairs=0
+        for x in counter:
+            if k != 0 and (x + k) in counter:
+                pairs+=1
+            elif k==0 and counter[x] >= 2:
+                    pairs+=1
+
+        return pairs

pascals-triangle.py

@@ -0,0 +1,21 @@
+class Solution:
+    def generate(self, numRows: int) -> List[List[int]]:
+
+        # time O(n^2), space O(1)
+        res = []
+        for i in range(1,numRows+1):
+            row = [1]*i
+            # always start at first 2 positions of prev row
+            l=0
+            r=1
+            if i > 2:
+                prevRow = res[-1]
+                p = 1
+                while r < len(prevRow):
+                    row[p] = prevRow[l]+prevRow[r] 
+                    p+=1
+                    l+=1
+                    r+=1
+            res.append(row)
+
+        return res