Merge pull request #169 from Abhi-sheKkK/union_of_two_lists

Union of two lists

python/union_of_two_lists.py

@@ -0,0 +1,55 @@
+'''
+Question : We have been given two sorted lists . We have to result a new list which is sorted 
+and also the union of the two given lists .
+Example  : input a = [1,1,2,3,4,5] , b= [1,2,7,8]
+            Output r=[1,2,3,4,5,7,8]
+Approach : We will use two pointers method for this , i for list a and j for list b.
+           If a[i] is less than b[j], add a[i] to the result if it's not already added, then move i.
+           If a[i] is greater than b[j], add b[j] to the result if it's not already added, then move j.
+           If a[i] equals b[j], add one of them and move both pointers.
+           After one of the arrays is exhausted, add the remaining unique elements from the other array.
+           The result will be the sorted union of the two arrays with unique elements.
+
+
+'''
+
+class Solution:
+
+    #Function to return a list containing the union of the two arrays.
+    def findUnion(self,a,b):
+        # code here 
+        i, j = 0, 0
+        result = []
+
+        # Traverse both arrays
+        while i < len(a) and j < len(b):
+            # If the current element in a[] is smaller, add it to the result if unique and move pointer i
+            if a[i] < b[j]:
+                if len(result) == 0 or result[-1] != a[i]:
+                    result.append(a[i])
+                i += 1
+            # If the current element in b[] is smaller, add it to the result if unique and move pointer j
+            elif a[i] > b[j]:
+                if len(result) == 0 or result[-1] != b[j]:
+                    result.append(b[j])
+                j += 1
+            # If both elements are equal, add only one of them if unique and move both pointers
+            else:
+                if len(result) == 0 or result[-1] != a[i]:
+                    result.append(a[i])
+                i += 1
+                j += 1
+
+        # Add remaining elements from a[]
+        while i < len(a):
+            if result[-1] != a[i]:
+                result.append(a[i])
+            i += 1
+
+        # Add remaining elements from b[]
+        while j < len(b):
+            if result[-1] != b[j]:
+                result.append(b[j])
+            j += 1
+
+        return result