Write Test Cases for Cards

HardPython

Problem

Principal Financial Group's QA automation may receive a shuffled set of card identities representing a physical card-checking process. There are 103 face-down cards: 51 card identities appear exactly twice, and one identity appears exactly once. You may reveal only one card at a time.

Implement find_odd_card(cards) to return the unpaired card identity and the minimum number of flips required to guarantee finding it. Because an unseen card could still be the missing match, the algorithm must provide a worst-case guarantee rather than stopping when a candidate first appears.

Formal Specification

Input: cards, a list of integers containing 2k + 1 values. Every value appears exactly twice except one value, which appears once.
Output: A two-element list [odd_card, flips], where odd_card is the value appearing once and flips is the minimum number of cards that must be revealed in the worst case.
The standard deck configuration uses k = 51, so there are 103 cards.

Constraints

1 <= k <= 10^6
len(cards) = 2k + 1
0 <= cards[i] < 2^31
Exactly one value appears once
Every other value appears exactly twice

Function Signature

def find_odd_card(cards):

Formal Specification

Input: cards, a list of integers containing 2k + 1 values. Every value appears exactly twice except one value, which appears once.
Output: A two-element list [odd_card, flips], where odd_card is the value appearing once and flips is the minimum number of cards that must be revealed in the worst case.
The standard deck configuration uses k = 51, so there are 103 cards.