leetcode_min_swaps_palindrome.py

from collections import Counter
import sys

''' minimum swaps to make string palindrome'''

# Function to Count minimum swap
def CountSwap(s, n):
    s = list(s)

    # Counter to count minimum swap
    count = 0
    ans = True

    # A loop which run in half string
    # from starting
    for i in range(n // 2):

        # Left pointer
        left = i

        # Right pointer
        right = n - left - 1

        # A loop which run from right pointer
        # to left pointer
        while left < right:

            # if both char same then
            # break the loop if not
            # same then we have to move
            # right pointer to one step left
            if s[left] == s[right]:
                break
            else:
                right -= 1

        # it denotes both pointer at
        # same position and we don't
        # have sufficient char to make
        # palindrome string
        if left == right:
            ans = False
            break
        else:
            for j in range(right, n - left - 1):
                (s[j], s[j + 1]) = (s[j + 1], s[j])
                count += 1
    if ans:
        return (count)
    else:
        return -1



def main():
    # Driver Code
    s = sys.stdin.readline().strip()

    # Legth of string
    n = len(s)

    # Function calling
    ans1 = CountSwap(s, n)
    ans2 = CountSwap(s[::-1], n)
    print(max(ans1, ans2))


if __name__ == "__main__":
    main()