On a table are
N cards, with a positive integer printed on the front and back of each card (possibly different).
We flip any number of cards, and after we choose one card.
If the number
X on the back of the chosen card is not on the front of any card, then this number X is good.
What is the smallest number that is good? If no number is good, output
backs[i] represent the number on the front and back of card
A flip swaps the front and back numbers, so the value on the front is now on the back and vice versa.
Input: fronts = [1,2,4,4,7], backs = [1,3,4,1,3] Output:
2Explanation: If we flip the second card, the fronts are
[1,3,4,4,7]and the backs are
[1,2,4,1,3]. We choose the second card, which has number 2 on the back, and it isn't on the front of any card, so
1 <= fronts.length == backs.length <= 1000.
1 <= fronts[i] <= 2000.
1 <= backs[i] <= 2000.