algorithms

commit 9b6e2d120e2ac998acad4c90f755ebd8a6e6fb46
parent cd956f6d2ffd2b8679c841d2bf4876442eceda64
Author: Andrew Laack <andrew@laack.co>
Date:   Fri, 11 Sep 2026 16:39:09 -0500

Two problems from contest

Diffstat:
A
count-good-cyclic-rotations/count-good-cyclic-rotations.py
 | 
27
+++++++++++++++++++++++++++
A
count-rotations-with-exactly-k-equal-adjacent-pairs/count-rotations-with-exactly-k-equal-adjacent-pairs.py
 | 
23
+++++++++++++++++++++++

2 files changed, 50 insertions(+), 0 deletions(-)
diff --git a/count-good-cyclic-rotations/count-good-cyclic-rotations.py b/count-good-cyclic-rotations/count-good-cyclic-rotations.py
@@ -0,0 +1,27 @@
+class Solution:
+    def countGoodRotations(self, nums: list[int]) -> int:
+        sc = 0
+        bound = len(nums) // 2
+        nl = len(nums)
+        
+        delta = 0
+        
+        for idx in range(0,len(nums)):
+            new_pos = ((idx) + nl) % nl
+            if new_pos < bound:
+                delta += nums[idx]
+            else:
+                delta -= nums[idx]
+
+        if delta > 0:
+            sc += 1
+
+        for pivot in range(1,len(nums)):
+            join_right = nums[pivot-1]
+            join_left = nums[(((pivot - 1) + bound)) % nl]
+            
+            delta += (join_left - join_right) * 2
+            if delta > 0:
+                sc += 1
+
+        return sc
diff --git a/count-rotations-with-exactly-k-equal-adjacent-pairs/count-rotations-with-exactly-k-equal-adjacent-pairs.py b/count-rotations-with-exactly-k-equal-adjacent-pairs/count-rotations-with-exactly-k-equal-adjacent-pairs.py
@@ -0,0 +1,23 @@
+class Solution:
+
+    def prefix_append(self,num,s):
+        pre = s[0:num]
+        s = s[num:len(s)] + pre
+        return s
+    def score(self,s):
+        sc = 0
+        for i in range(0,len(s) - 1):
+            if s[i] == s[i+1]:
+                sc += 1
+        return sc
+        
+    def countRotations(self, s: str, k: int) -> int:
+        # string s length n, int k
+        # choose prefix of s and move it to the end of string
+        # score = number of i where i == i+1
+        score = 0
+        for n in range(0,len(s)):
+            re = self.prefix_append(n,s)
+            if self.score(re) == k:
+                score += 1
+        return score