Create odd-even-jump.py

Author: kamyu104

Python/odd-even-jump.py

@@ -0,0 +1,31 @@
+# Time:  O(nlogn)
+# Space: O(n)
+
+class Solution(object):
+    def oddEvenJumps(self, A):
+        """
+        :type A: List[int]
+        :rtype: int
+        """
+        def findNext(idx):
+            result = [None]*len(idx)
+            stack = []
+            for i in idx:
+                while stack and stack[-1] < i:
+                    result[stack.pop()] = i
+                stack.append(i)
+            return result
+        
+        idx = sorted(range(len(A)), key = lambda i: A[i])
+        next_higher = findNext(idx)
+        idx.sort(key = lambda i: -A[i])
+        next_lower = findNext(idx)
+
+        odd, even = [False]*len(A), [False]*len(A)
+        odd[-1], even[-1] = True, True
+        for i in reversed(xrange(len(A)-1)):
+            if next_higher[i]:
+                odd[i] = even[next_higher[i]]
+            if next_lower[i]:
+                even[i] = odd[next_lower[i]]
+        return sum(odd)