How often will a double flop be the same rank

main.go

package main

import (
	"fmt"
	"math/rand"
	"sort"
	"time"
)

func createDeck() *[52]int {
	var deck [52]int

	for i := 0; i < 52; i++ {
		deck[i] = i
	}
	return &deck
}

func shuffleDeck(a *[52]int) {
	rand.Seed(time.Now().UnixNano())
	rand.Shuffle(len(a), func(i, j int) { a[i], a[j] = a[j], a[i] })
}

/*
For these purposes, we will rank A as 1, 2 as 2, ... K as 13.
*/
func getRankOfFlop(flop []int) []int {
	// var flopRank []int
	flopRank := make([]int, 3)

	for i, card := range flop {
		// Adding 1 so we go from 1-13 instead of 0-12.
		flopRank[i] = (card % 13) + 1
	}
	return flopRank
}

func main() {
	numOfRuns := 10000000

	deck := createDeck()

	numOfMatchingFlops := 0

	for i := 0; i < numOfRuns; i++ {

		shuffleDeck(deck)

		// First three cards
		firstFlop := deck[0:3]
		secondFlop := deck[3:6]

		firstFlopRank := getRankOfFlop(firstFlop)
		secondFlopRank := getRankOfFlop(secondFlop)

		sort.Ints(firstFlopRank)
		sort.Ints(secondFlopRank)

		matchingFlop := true
		for j := 0; j < 3; j++ {
			if firstFlopRank[j] != secondFlopRank[j] {
				matchingFlop = false
				break
			}
		}
		if matchingFlop {
			numOfMatchingFlops += 1
		}
	}

	fmt.Println("Number of matching flops: ", numOfMatchingFlops)
	fmt.Println("Percentage: ", fmt.Sprintf("%.2f", float64(numOfMatchingFlops)/float64(numOfRuns)*100), "%")
}