https://leetcode.com/problems/minimum-domino-rotations-for-equal-row

Given 2 arrays a and b, each containing n integers. You can swap elements at the same index. Return the minimum number of swaps needed for all elements in either a or b to be the same or -1 if that is not possible.

Example 1:

Input:
a = [1, 2, 3, 6, 3, 2]
b = [2, 1, 2, 2, 2, 4]

Output: 2

Explanation:
You can swap elements at index 1 and 5, so that all elements in b will be equal to 2.
a = [1, 1, 3, 6, 3, 4]
b = [2, 2, 2, 2, 2, 2]

Example 2:

Input:
a = [1, 2, 1, 2]
b = [2, 6, 1, 2]

Output: -1

Example 3:

Input:
a = [1, 2, 1, 3]
b = [1, 1, 2, 1]

Output: 1

Constraints:

• n is an integer within the range [1..100,000];
• each element of arrays a and b is an integer within the range [1..6].