Update minimum-absolute-difference-queries.py

Author: kamyu104

Python/minimum-absolute-difference-queries.py

@@ -1,24 +1,28 @@
 # Time:  O(r * (n + q)), r is the max of nums
 # Space: O(r * n)
 
-import itertools
-
-
 class Solution(object):
     def minDifference(self, nums, queries):
         """
         :type nums: List[int]
         :type queries: List[List[int]]
         :rtype: List[int]
         """
+        INF = float("inf")
         prefix = [[0]*(max(nums)+1)]
         for num in nums:
             prefix.append(prefix[-1][:])
             prefix[-1][num] += 1
         result = []
         for l, r in queries:
-            sub_nums = [num for cnt1, cnt2, num in itertools.izip(prefix[l], prefix[r+1], xrange(len(prefix[0]))) if cnt1 < cnt2]
-            result.append(min([b-a for a, b in itertools.izip(sub_nums, itertools.islice(sub_nums, 1, len(sub_nums)))] or [-1]))
+            min_diff, prev = INF, -1
+            for num in xrange(len(prefix[0])):
+                if not (prefix[l][num] < prefix[r+1][num]):
+                    continue
+                if prev != -1:
+                    min_diff = min(min_diff, num-prev)
+                prev = num
+            result.append(min_diff if min_diff != INF else -1)
         return result
 
 
@@ -43,9 +47,10 @@ def minDifference(self, nums, queries):
             min_diff, prev = INF, -1
             for num in xrange(len(idxs)):
                 i = bisect.bisect_left(idxs[num], l)
-                if i < len(idxs[num]) and idxs[num][i] <= r:
-                    if prev != -1:
-                        min_diff = min(min_diff, num-prev)
-                    prev = num
+                if not (i < len(idxs[num]) and idxs[num][i] <= r):
+                    continue
+                if prev != -1:
+                    min_diff = min(min_diff, num-prev)
+                prev = num
             result.append(min_diff if min_diff != INF else -1)
         return result