LeetCode Weekly Contest 177

func daysBetweenDates(date1 string, date2 string) int {
    t1, _ := time.Parse("2006-01-02", date1)
    t2, _ := time.Parse("2006-01-02", date2)
    ans := t1.Sub(t2).Hours()
    if ans > 0 {
    return int(ans) / 24
    }
    return -int(ans) / 24
}

// TODO

func closestDivisors(num int) []int {
    num1, num2 := num+1, num+2
    for ans := int(math.Sqrt(float64(num2))); ans > 0; ans-- {
    if (num1)%ans == 0 {
    return []int{ans, num1 / ans}
    } else if (num2)%ans == 0 {
    return []int{ans, num2 / ans}
    }
    }
    return []int{}
}

func largestMultipleOfThree(digits []int) string {
    // 先处理特殊情况
    s := sum(digits)
    if s == 0 {
    return "0"
    } else if s%3 == 0 {
    return genMaxString(digits)
    }

    // 余数分类
    remainder := make([][]int, 3) 
    for i := range remainder {
    remainder[i] = []int{}
    }
    for i := range digits {
    mod := digits[i] % 3
    remainder[mod] = append(remainder[mod], digits[i])
    }

    // 在可拿的情况下，保证拿的都是最大的
    sort.Ints(remainder[1])
    sort.Ints(remainder[2])

    resDigits := remainder[0] // 以余 0 为基础

    len1, len2 := len(remainder[1]), len(remainder[2])

    // 尽可能的多拿，[1,1,1,2]
    if s%3 == 1 {
    if len1 > 0 {
    remainder[1][0] = -1 // -1 代表删除
    } else if len2 > 1 {
    remainder[2][0] = -1
    remainder[2][1] = -1
    }
    } else {
    if len2 > 0 {
    remainder[2][0] = -1
    } else if len1 > 1 {
    remainder[1][0] = -1
    remainder[1][1] = -1
    }
    }
    resDigits = append(resDigits, remainder[1]...)
    resDigits = append(resDigits, remainder[2]...)
    return genMaxString(resDigits)
}

func sum(nums []int) int {
    ans := 0
    for i := range nums {
    ans += nums[i]
    }
    return ans
}

func genMaxString(nums []int) string {
    ans := ""
    sort.Sort(sort.IntSlice(nums))
    for i := 0; i < len(nums); i++ {
    if nums[i] == -1 { // -1 代表删除
    continue
    }
    ans = strconv.Itoa(nums[i]) + ans
    }
    return ans
}