Create replace-elements-in-an-array.py

Python/replace-elements-in-an-array.py

@@ -0,0 +1,34 @@
+# Time:  O(n + m)
+# Space: O(n)
+
+# hash table, optimized from solution2
+class Solution(object):
+    def arrayChange(self, nums, operations):
+        """
+        :type nums: List[int]
+        :type operations: List[List[int]]
+        :rtype: List[int]
+        """
+        lookup = {x:i for i, x in enumerate(nums)}
+        for x, y in operations:
+            lookup[y] = lookup.pop(x)
+        for x, i in lookup.iteritems():
+            nums[i] = x
+        return nums
+
+
+# Time:  O(n + m)
+# Space: O(n)
+# hash table
+class Solution2(object):
+    def arrayChange(self, nums, operations):
+        """
+        :type nums: List[int]
+        :type operations: List[List[int]]
+        :rtype: List[int]
+        """
+        lookup = {x:i for i, x in enumerate(nums)}
+        for x, y in operations:
+            nums[lookup[x]] = y
+            lookup[y] = lookup.pop(x)
+        return nums