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3348. Smallest Divisible Digit Product II

Description

You are given a string num which represents a positive integer, and an integer t.

A number is called zero-free if none of its digits are 0.

Return a string representing the smallest zero-free number greater than or equal to num such that the product of its digits is divisible by t. If no such number exists, return "-1".

 

Example 1:

Input: num = "1234", t = 256

Output: "1488"

Explanation:

The smallest zero-free number that is greater than 1234 and has the product of its digits divisible by 256 is 1488, with the product of its digits equal to 256.

Example 2:

Input: num = "12355", t = 50

Output: "12355"

Explanation:

12355 is already zero-free and has the product of its digits divisible by 50, with the product of its digits equal to 150.

Example 3:

Input: num = "11111", t = 26

Output: "-1"

Explanation:

No number greater than 11111 has the product of its digits divisible by 26.

 

Constraints:

  • 2 <= num.length <= 2 * 105
  • num consists only of digits in the range ['0', '9'].
  • num does not contain leading zeros.
  • 1 <= t <= 1014

Solutions

Solution 1

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func smallestNumber(num string, t int64) string {
    primeCount, isDivisible := getPrimeCount(t)
    if !isDivisible {
        return "-1"
    }

    factorCount := getFactorCount(primeCount)
    if sumValues(factorCount) > len(num) {
        return construct(factorCount)
    }

    primeCountPrefix := getPrimeCountFromString(num)
    firstZeroIndex := strings.Index(num, "0")
    if firstZeroIndex == -1 {
        firstZeroIndex = len(num)
        if isSubset(primeCount, primeCountPrefix) {
            return num
        }
    }

    for i := len(num) - 1; i >= 0; i-- {
        d := int(num[i] - '0')
        primeCountPrefix = subtract(primeCountPrefix, kFactorCounts[d])
        spaceAfterThisDigit := len(num) - 1 - i
        if i > firstZeroIndex {
            continue
        }
        for biggerDigit := d + 1; biggerDigit < 10; biggerDigit++ {
            factorsAfterReplacement := getFactorCount(
                subtract(subtract(primeCount, primeCountPrefix), kFactorCounts[biggerDigit]),
            )
            if sumValues(factorsAfterReplacement) <= spaceAfterThisDigit {
                fillOnes := spaceAfterThisDigit - sumValues(factorsAfterReplacement)
                return num[:i] + strconv.Itoa(biggerDigit) + strings.Repeat("1", fillOnes) + construct(factorsAfterReplacement)
            }
        }
    }

    factorsAfterExtension := getFactorCount(primeCount)
    return strings.Repeat("1", len(num)+1-sumValues(factorsAfterExtension)) + construct(factorsAfterExtension)
}

var kFactorCounts = map[int]map[int]int{
    0: {}, 1: {}, 2: {2: 1}, 3: {3: 1}, 4: {2: 2},
    5: {5: 1}, 6: {2: 1, 3: 1}, 7: {7: 1}, 8: {2: 3}, 9: {3: 2},
}

func getPrimeCount(t int64) (map[int]int, bool) {
    count := map[int]int{2: 0, 3: 0, 5: 0, 7: 0}
    for _, prime := range []int{2, 3, 5, 7} {
        for t%int64(prime) == 0 {
            t /= int64(prime)
            count[prime]++
        }
    }
    return count, t == 1
}

func getPrimeCountFromString(num string) map[int]int {
    count := map[int]int{2: 0, 3: 0, 5: 0, 7: 0}
    for _, d := range num {
        for prime, freq := range kFactorCounts[int(d-'0')] {
            count[prime] += freq
        }
    }
    return count
}

func getFactorCount(count map[int]int) map[int]int {
    res := map[int]int{}
    count8 := count[2] / 3
    remaining2 := count[2] % 3
    count9 := count[3] / 2
    count3 := count[3] % 2
    count4 := remaining2 / 2
    count2 := remaining2 % 2
    count6 := 0
    if count2 == 1 && count3 == 1 {
        count2, count3 = 0, 0
        count6 = 1
    }
    if count3 == 1 && count4 == 1 {
        count2 = 1
        count6 = 1
        count3, count4 = 0, 0
    }
    res[2] = count2
    res[3] = count3
    res[4] = count4
    res[5] = count[5]
    res[6] = count6
    res[7] = count[7]
    res[8] = count8
    res[9] = count9
    return res
}

func construct(factors map[int]int) string {
    var res strings.Builder
    for digit := 2; digit < 10; digit++ {
        res.WriteString(strings.Repeat(strconv.Itoa(digit), factors[digit]))
    }
    return res.String()
}

func isSubset(a, b map[int]int) bool {
    for key, value := range a {
        if b[key] < value {
            return false
        }
    }
    return true
}

func subtract(a, b map[int]int) map[int]int {
    res := make(map[int]int, len(a))
    for k, v := range a {
        res[k] = v
    }
    for k, v := range b {
        res[k] = max(0, res[k]-v)
    }
    return res
}

func sumValues(count map[int]int) int {
    sum := 0
    for _, v := range count {
        sum += v
    }
    return sum
}

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