Count Number of Swaps to Change One List to Another in Python

Suppose we have two lists of numbers L1 and L2, the length of each list is n and each value is unique to its list, and values are in range 1 to n, we have to find the minimum number of adjacent swaps required to transform L1 to L2.

So, if the input is like L1 = [0, 1, 2, 3] L2 = [2, 0, 1, 3], then the output will be 2, as we can swap 1 and 2, L1 will be [0, 2, 1, 3], and then 0 and 2, L1 will be [2, 0, 1, 3], this is same as L2.

To solve this, we will follow these steps:

• ans := 0

• for each req in L2, do

  • i := index of req in L1

  • delete ith element from L1

  • ans := ans + i

• return ans

Let us see the following implementation to get better understanding:

Example

 Live Demo

class Solution:
   def solve(self, L1, L2):
      ans = 0
      for req in L2:
         i = L1.index(req)
         L1.pop(i)
         ans += i
      return ans

ob = Solution()
L1 = [0, 1, 2, 3]
L2 = [2, 0, 1, 3]
print(ob.solve(L1, L2))

Input

[0, 1, 2, 3],[2, 0, 1, 3]

Output

2