91 lines
2.9 KiB
Markdown
91 lines
2.9 KiB
Markdown
# Single Poker Hand Ranking Service
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## Requirements
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This service comprises an API to compute the rank of an individual poker hand. The requirements are to:
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- Write an algorithm that takes a hand of cards and identifies the ranking of the given hand.
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- Expose an API to serve this algorithm via an endpoint `/rank`, that accepts a valid poker hand and returns its ranking.
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- Rank information should be formatted as `<rank_name>: <description>`, see description format for each different rank below.
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## Poker Rules
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A poker hand consists of 5 cards dealt from a deck. A deck is composed of 52 cards ordered as `2 through 10`, `J` (*Jack*), `Q` (*Queen*), `K` (*King*), and `A` (*Ace*); and split across 4 suits: *♠ Spades* (black), *♦ Diamonds* (red), *♣ Clubs* (black), and *♥ Hearts* (red).
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Poker hands are ranked by the following partial order from highest to lowest:
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**1. Royal Flush** ~ `[ A♥ K♥ Q♥ J♥ 10♥ ]`
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The best hand possible, a royal flush consists of A, K, Q, J and 10, all of the same suit.
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Description format: `<suit>`
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**2. Straight Flush** ~ `[ 6♥ 7♥ 8♥ 9♥ 10♥ ]`
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Also very rare, a straight flush consists of any straight that is all the same suit. Note Ace can act as value `1` to form a straight with values `2 3 4 5`.
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Description format: `<highest_value>-high <suit>`
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**3. Four of a Kind** ~ `[ A♥ A♣ A♦ A♠ K♥ ]`
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Four of a kind, or 'quads', consists of four cards of equal value along with another card known as a side card.
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Description format: `<quads value>`
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**4. Full House** ~ `[ A♥ A♣ A♦ K♠ K♥ ]`
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A full house consists of three cards of one value and two cards of another.
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Description format: `<trips_value> over <pair_value>`
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**5. FLush** ~ `[ K♣ 10♣ 8♣ 7♣ 5♣ ]`
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A flush is a hand which has all cards of the same suit.
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Description format: `<suit>`
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**6. Straight** ~ `[ 10♥ 9♣ 8♦ 7♠ 6♥ ]`
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A straight has five cards of consecutive value that are not all the same suit. Note Ace can act as value `1` to form a straight with values `2 3 4 5`.
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Description format: `<highest_value>-high`
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**7. Three of a Kind** ~ `[ A♥ A♣ A♦ K♠ Q♥ ]`
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Also known as 'trips', three of a kind is 3 cards of the same value and 2 side cards of different values.
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Description format: `<trips value>`
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**8. Two Pair** ~ `[ A♥ A♣ K♦ K♠ 7♥ ]`
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Two pair cosists of two cards of the same value, and three extra cards.
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Description format: `<high_pair_value> and <low_pair_value>`
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**9. Pair** ~ `[ A♥ A♣ K♦ J♠ 7♥ ]`
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One pair consists of two cards of the same value, and three extra cards.
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Description format: `<pair_value>`
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**10. High Card** ~ `[ A♥ K♣ Q♦ 9♠ 7♥ ]`
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Five cards that do not interact with each other to make any of the above hands.
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Description format: `<value>`
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## Examples
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```
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Query: "2H 3D 5S 9C KD"
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Result: "high card: King"
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~
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Query: "2H 4D 4S 2C 4H"
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Result: "full house: 4 over 2"
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~
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Query: "6H 7H 8H 9H 10H"
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Result: "straight flush: 10-high diamonds"
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```
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