seg 0s and 1s

Author: harishpuvvada

Lists/segregate 0s and 1s.py

@@ -0,0 +1,27 @@
+def segregate0and1(arr, size): '''Time complexity is O(n)'''
+    # Initialize left and right indexes
+    left, right = 0, size-1
+
+    while left < right:
+        # Increment left index while we see 0 at left
+        while arr[left] == 0 and left < right:
+            left += 1
+
+        # Decrement right index while we see 1 at right
+        while arr[right] == 1 and left < right:
+            right -= 1
+
+        # If left is smaller than right then there is a 1 at left
+        # and a 0 at right. Exchange arr[left] and arr[right]
+        if left < right:
+            arr[left] = 0   #instead of swap, we can just assign 0 and 1 here
+            arr[right] = 1
+            left += 1        #since value at this index is now okay, we can inc/dec them
+            right -= 1
+
+    return arr
+
+arr = [0, 1, 0, 1, 1, 1]
+arr_size = len(arr)
+print("Array after segregation")
+print(segregate0and1(arr, arr_size))