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Author: Chris Wu

problems/move-zeroes.py

@@ -18,4 +18,23 @@ def moveZeroes(self, nums):
                 temp = nums[cursor]
                 nums[cursor] = nums[i]
                 nums[i] = temp
-                cursor+=1
+                cursor+=1
+
+
+"""
+j is the index to insert when a number not equal to 0.
+After all the non-zero numbers are inplace, the rests are all zeros.
+"""
+class Solution(object):
+    def moveZeroes(self, nums):
+        j = 0
+        
+        for n in nums:
+            if n!=0:
+                nums[j] = n
+                j += 1
+        
+        for i in xrange(j, len(nums)):
+            nums[i] = 0
+        
+        return nums

problems/remove-duplicates-from-sorted-array-ii.py

@@ -0,0 +1,14 @@
+"""
+j is the index to insert when a "new" number are found.
+For each iteration, nums[:j] is the output result we currently have.
+So nums[i] should check with nums[j-1] and nums[j-2].
+"""
+class Solution(object):
+    def removeDuplicates(self, nums):
+        j = 2
+        
+        for i in xrange(2, len(nums)):
+            if not (nums[i]==nums[j-1] and nums[i]==nums[j-2]):
+                nums[j] = nums[i]
+                j += 1
+        return j

problems/remove-element.py

@@ -0,0 +1,12 @@
+"""
+j is the index to insert when a number not equal to val.
+j will never catch up i, so j will not mess up the check.
+"""
+class Solution(object):
+    def removeElement(self, nums, val):
+        j = 0
+        for n in nums:
+            if n!=val:
+                nums[j] = n
+                j += 1
+        return j