Task: Poker hand analyser
C: #include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>

#define TRUE 1
#define FALSE 0

#define FACES "23456789tjqka"
#define SUITS "shdc"

typedef int bool;

typedef struct {
    int face;  
    char suit;
} card;

card cards[5];

int compare_card(const void *a, const void *b) {
    card c1 = *(card *)a;
    card c2 = *(card *)b;
    return c1.face - c2.face;
}

bool equals_card(card c1, card c2) {
    if (c1.face == c2.face && c1.suit == c2.suit) return TRUE;
    return FALSE;
}

bool are_distinct() {
    int i, j;
    for (i = 0; i < 4; ++i)
        for (j = i + 1; j < 5; ++j)
            if (equals_card(cards[i], cards[j])) return FALSE;
    return TRUE;
}

bool is_straight() {
    int i;
    qsort(cards, 5, sizeof(card), compare_card);
    if (cards[0].face + 4 == cards[4].face) return TRUE;
    if (cards[4].face == 12 && cards[0].face == 0 &&
        cards[3].face == 3) return TRUE;
    return FALSE;
}

bool is_flush() {
    int i;
    char suit = cards[0].suit;
    for (i = 1; i < 5; ++i) if (cards[i].suit != suit) return FALSE;
    return TRUE;
}

const char *analyze_hand(const char *hand) {
    int i, j, gs = 0;
    char suit, *cp;
    bool found, flush, straight;
    int groups[13];
    if (strlen(hand) != 14) return "invalid";
    for (i = 0; i < 14; i += 3) {
        cp = strchr(FACES, tolower(hand[i]));
        if (cp == NULL) return "invalid";
        j = i / 3;
        cards[j].face = cp - FACES;
        suit = tolower(hand[i + 1]);
        cp = strchr(SUITS, suit);
        if (cp == NULL) return "invalid";
        cards[j].suit = suit;
    }
    if (!are_distinct()) return "invalid";
    for (i = 0; i < 13; ++i) groups[i] = 0;
    for (i = 0; i < 5; ++i) groups[cards[i].face]++;
    for (i = 0; i < 13; ++i) if (groups[i] > 0) gs++;
    switch(gs) {
        case 2:
            found = FALSE;
            for (i = 0; i < 13; ++i) if (groups[i] == 4) {
                found = TRUE;
                break;
            }
            if (found) return "four-of-a-kind";
            return "full-house";
        case 3:
            found = FALSE;
            for (i = 0; i < 13; ++i) if (groups[i] == 3) {
                found = TRUE;
                break;
            }
            if (found) return "three-of-a-kind";
            return "two-pairs";
        case 4:
            return "one-pair";
        default:
            flush = is_flush();
            straight = is_straight();
            if (flush && straight)
                return "straight-flush";
            else if (flush)
                return "flush";
            else if (straight)
                return "straight";
            else
                return "high-card";
    }
}

int main(){
    int i;
    const char *type;
    const char *hands[10] = {
        "2h 2d 2c kc qd",
        "2h 5h 7d 8c 9s",
        "ah 2d 3c 4c 5d",
        "2h 3h 2d 3c 3d",
        "2h 7h 2d 3c 3d",
        "2h 7h 7d 7c 7s",
        "th jh qh kh ah",
        "4h 4s ks 5d ts",
        "qc tc 7c 6c 4c",
        "ah ah 7c 6c 4c"
    };
    for (i = 0; i < 10; ++i) {
        type = analyze_hand(hands[i]);
        printf("%s: %s\n", hands[i], type);
    }
    return 0;
}

Go: package main

import (
    "fmt"
    "sort"
    "strings"
)

type card struct {
    face byte
    suit byte
}

const faces = "23456789tjqka"
const suits = "shdc"

func isStraight(cards []card) bool {
    sorted := make([]card, 5)
    copy(sorted, cards)
    sort.Slice(sorted, func(i, j int) bool {
        return sorted[i].face < sorted[j].face
    })
    if sorted[0].face+4 == sorted[4].face {
        return true
    }
    if sorted[4].face == 14 && sorted[0].face == 2 && sorted[3].face == 5 {
        return true
    }
    return false
}

func isFlush(cards []card) bool {
    suit := cards[0].suit
    for i := 1; i < 5; i++ {
        if cards[i].suit != suit {
            return false
        }
    }
    return true
}

func analyzeHand(hand string) string {
    temp := strings.Fields(strings.ToLower(hand))
    splitSet := make(map[string]bool)
    var split []string
    for _, s := range temp {
        if !splitSet[s] {
            splitSet[s] = true
            split = append(split, s)
        }
    }
    if len(split) != 5 {
        return "invalid"
    }
    var cards []card

    for _, s := range split {
        if len(s) != 2 {
            return "invalid"
        }
        fIndex := strings.IndexByte(faces, s[0])
        if fIndex == -1 {
            return "invalid"
        }
        sIndex := strings.IndexByte(suits, s[1])
        if sIndex == -1 {
            return "invalid"
        }
        cards = append(cards, card{byte(fIndex + 2), s[1]})
    }

    groups := make(map[byte][]card)
    for _, c := range cards {
        groups[c.face] = append(groups[c.face], c)
    }

    switch len(groups) {
    case 2:
        for _, group := range groups {
            if len(group) == 4 {
                return "four-of-a-kind"
            }
        }
        return "full-house"
    case 3:
        for _, group := range groups {
            if len(group) == 3 {
                return "three-of-a-kind"
            }
        }
        return "two-pair"
    case 4:
        return "one-pair"
    default:
        flush := isFlush(cards)
        straight := isStraight(cards)
        switch {
        case flush && straight:
            return "straight-flush"
        case flush:
            return "flush"
        case straight:
            return "straight"
        default:
            return "high-card"
        }
    }
}

func main() {
    hands := [...]string{
        "2h 2d 2c kc qd",
        "2h 5h 7d 8c 9s",
        "ah 2d 3c 4c 5d",
        "2h 3h 2d 3c 3d",
        "2h 7h 2d 3c 3d",
        "2h 7h 7d 7c 7s",
        "th jh qh kh ah",
        "4h 4s ks 5d ts",
        "qc tc 7c 6c 4c",
        "ah ah 7c 6c 4c",
    }
    for _, hand := range hands {
        fmt.Printf("%s: %s\n", hand, analyzeHand(hand))
    }
}