TDD coding kata - bulls and cows

  • Leetcode url

    https://leetcode.com/problems/bulls-and-cows/description/

  • Test Code

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    import (
    	"testing"
    	"github.com/stretchr/testify/assert"
    )

    func TestGuessAllCorrect(t *testing.T) {
    	t.Run("guess4BullsAndNoCows", func(t *testing.T) {
    		ret := getHint("1111", "1111")
    		assert.Equal(t, "4A0B", ret, "guess4BullsAndNoCows failed")
    	})

    	t.Run("guessNoBullsAndCows", func(t *testing.T) {
    		ret := getHint("1111", "2222")
    		assert.Equal(t, "0A0B", ret, "guessNoBullsAndCows failed")
    	})

    	t.Run("guessOneBullAndNoCow", func(t *testing.T) {
    		ret := getHint("1111", "1222")
    		assert.Equal(t, "1A0B", ret, "guessOneBullAndNoCow failed")
    	})

    	t.Run("guessOneBullAndOneCow", func(t *testing.T) {
    		ret := getHint("1112", "1323")
    		assert.Equal(t, "1A1B", ret, "guessOneBullAndOneCow failed")
    	})

    	t.Run("guessOneBullAndOneCowWithDuplicateGuessNumber", func(t *testing.T) {
    		ret := getHint("1112", "1223")
    		assert.Equal(t, "1A1B", ret, "guessOneBullAndOneCowWithDuplicateGuessNumber failed")
    	})

    	t.Run("guessNoBullAndOneCowWithDuplicateGuessNumber", func(t *testing.T) {
    		ret := getHint("1234", "0111")
    		assert.Equal(t, "0A1B", ret, "guessNoBullAndOneCowWithDuplicateGuessNumber failed")
    	})

    	t.Run("guessNoBullAndFourCowWithDuplicateDigital", func(t *testing.T) {
    		ret := getHint("1122", "2211")
    		assert.Equal(t, "0A4B", ret, "guessNoBullAndFourCowWithDuplicateDigital failed")
    	})

    	t.Run("guessNoBullAndOneCowWithDuplicatePosition", func(t *testing.T) {
    		ret := getHint("1122", "0001")
    		assert.Equal(t, "0A1B", ret, "guessNoBullAndOneCowWithDuplicatePosition failed")
    	})
    }

  • 实现代码

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    import "fmt"

    func getHint(secret, guess string) string {
    	A := 0
    	B := 0

    	guessBytes := []byte(guess)
    	secretBytes := []byte(secret)
    	guessedByteMap := make(map[int]int)
    	secretByteMap := make(map[int]int)

    	for guestIndex, guestValue := range guessBytes {
    		if guestValue == secretBytes[guestIndex] {
    			setGuessAndSecretIndexPair(guessedByteMap, secretByteMap, guestIndex, guestIndex)
    			A = increaseBullNumber(A)
    		}
    	}

    	for guestIndex, guestValue := range guessBytes {
    		for secretIndex, secretValue := range secretBytes {
    			if guestIndex != secretIndex && guestValue == secretValue &&
    				checkSecretAndGuessIndexUsed(guessedByteMap, secretByteMap, guestIndex, secretIndex) {
    				B = increaseCowNumber(B)
    				setGuessAndSecretIndexPair(guessedByteMap, secretByteMap, guestIndex, secretIndex)

    			}
    		}
    	}

    	return fmt.Sprintf("%dA%dB", A, B)
    }

    func increaseBullNumber(a int) int {
    	return a + 1
    }

    func increaseCowNumber(b int) int {
    	return b + 1
    }

    func setGuessAndSecretIndexPair(guessedByteMap map[int]int, secretByteMap map[int]int, guestIndex, secretIndex int) {
    	guessedByteMap[guestIndex] = 1
    	secretByteMap[secretIndex] = 1
    }

    func checkSecretAndGuessIndexUsed(guessedByteMap, secretByteMap map[int]int, guestIndex, secretIndex int) bool {
    	return secretByteMap[secretIndex] == 0 && guessedByteMap[guestIndex] == 0
    }

    思路：遍历guess字符串两边，第一遍遍历产生bull个数，第二遍产生cows个数。需要两个map记录guess和secret被使用过的字符下标，避免重复计算