Create count-pairs-that-form-a-complete-day-i.py

Author: kamyu104

Python/count-pairs-that-form-a-complete-day-i.py

@@ -0,0 +1,28 @@
+# Time:  O(n + 24)
+# Space: O(24)
+
+# freq table
+class Solution(object):
+    def countCompleteDayPairs(self, hours):
+        """
+        :type hours: List[int]
+        :rtype: int
+        """
+        result = 0
+        cnt = [0]*24
+        for x in hours:
+            result += cnt[-x%24]
+            cnt[x%24] += 1
+        return result
+
+
+# Time:  O(n^2)
+# Space: O(1)
+# brute force
+class Solution2(object):
+    def countCompleteDayPairs(self, hours):
+        """
+        :type hours: List[int]
+        :rtype: int
+        """
+        return sum((hours[i]+hours[j])%24 == 0 for i in xrange(len(hours)-1) for j in xrange(i+1, len(hours)))