Task: Poker hand analyser
C++: #include <iostream>
#include <sstream>
#include <algorithm>
#include <vector>

using namespace std;

class poker
{
public:
    poker() { face = "A23456789TJQK"; suit = "SHCD"; }
    string analyze( string h )
    {
	memset( faceCnt, 0, 13 ); memset( suitCnt, 0, 4 ); vector<string> hand;
	transform( h.begin(), h.end(), h.begin(), toupper ); istringstream i( h );
	copy( istream_iterator<string>( i ), istream_iterator<string>(), back_inserter<vector<string> >( hand ) );
	if( hand.size() != 5 ) return "invalid hand."; vector<string>::iterator it = hand.begin();
	sort( it, hand.end() ); if( hand.end() != adjacent_find( it, hand.end() ) ) return "invalid hand.";
	while( it != hand.end() )
	{
	    if( ( *it ).length() != 2 ) return "invalid hand.";
	    int n = face.find( ( *it ).at( 0 ) ), l = suit.find( ( *it ).at( 1 ) );
	    if( n < 0 || l < 0 ) return "invalid hand.";
	    faceCnt[n]++; suitCnt[l]++; it++;
	}
	cout << h << ": "; return analyzeHand();
    }
private:
    string analyzeHand()
    {
	bool p1 = false, p2 = false, t = false, f = false, fl = false, st = false;
	for( int x = 0; x < 13; x++ )
	    switch( faceCnt[x] )
	    {
		case 2: if( p1 ) p2 = true; else p1 = true; break;
		case 3: t = true; break;
		case 4: f = true;
	    }
	for( int x = 0; x < 4; x++ )if( suitCnt[x] == 5 ){ fl = true; break; }

	if( !p1 && !p2 && !t && !f )
        {
	    int s = 0;
	    for( int x = 0; x < 13; x++ )
	    { 
		if( faceCnt[x] ) s++; else s = 0;
		if( s == 5 ) break;
	    }
	    st = ( s == 5 ) || ( s == 4 && faceCnt[0] && !faceCnt[1] );
	}

	if( st && fl ) return "straight-flush";
	else if( f ) return "four-of-a-kind"; 
	else if( p1 && t ) return "full-house";
	else if( fl ) return "flush";
	else if( st ) return "straight";
	else if( t ) return "three-of-a-kind";
	else if( p1 && p2 ) return "two-pair";
	else if( p1 ) return "one-pair";
        return "high-card";
    }
    string face, suit;
    unsigned char faceCnt[13], suitCnt[4];
};

int main( int argc, char* argv[] )
{
    poker p; 
    cout << p.analyze( "2h 2d 2s ks qd" ) << endl; cout << p.analyze( "2h 5h 7d 8s 9d" ) << endl;
    cout << p.analyze( "ah 2d 3s 4s 5s" ) << endl; cout << p.analyze( "2h 3h 2d 3s 3d" ) << endl;
    cout << p.analyze( "2h 7h 2d 3s 3d" ) << endl; cout << p.analyze( "2h 7h 7d 7s 7c" ) << endl;
    cout << p.analyze( "th jh qh kh ah" ) << endl; cout << p.analyze( "4h 4c kc 5d tc" ) << endl;
    cout << p.analyze( "qc tc 7c 6c 4c" ) << endl << endl; return system( "pause" );
}

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))
    }
}