2094-Finding3DigitEvenNumbers.go

package main

// 2094. Finding 3-Digit Even Numbers
// You are given an integer array digits, where each element is a digit. The array may contain duplicates.

// You need to find all the unique integers that follow the given requirements:
//     The integer consists of the concatenation of three elements from digits in any arbitrary order.
//     The integer does not have leading zeros.
//     The integer is even.

// For example, if the given digits were [1, 2, 3], integers 132 and 312 follow the requirements.

// Return a sorted array of the unique integers.

// Example 1:
// Input: digits = [2,1,3,0]
// Output: [102,120,130,132,210,230,302,310,312,320]
// Explanation: All the possible integers that follow the requirements are in the output array. 
// Notice that there are no odd integers or integers with leading zeros.

// Example 2:
// Input: digits = [2,2,8,8,2]
// Output: [222,228,282,288,822,828,882]
// Explanation: The same digit can be used as many times as it appears in digits. 
// In this example, the digit 8 is used twice each time in 288, 828, and 882. 

// Example 3:
// Input: digits = [3,7,5]
// Output: []
// Explanation: No even integers can be formed using the given digits.

// Constraints:
//     3 <= digits.length <= 100
//     0 <= digits[i] <= 9

import "fmt"

func findEvenNumbers(digits []int) []int {
    res, avail := []int{}, make([]int, 10)
    for _, digit := range digits {
        avail[digit]++
    }
    compare := func(avail, check []int) bool {
        for i := 0; i < 10; i++ {
            if check[i] > avail[i] { return false }
        }
        return true
    }
    check := func(num int) []int {
        res := make([]int, 10)
        for num != 0 {
            res[num % 10]++
            num /= 10
        }
        return res
    }
    for num := 100; num < 1000; num += 2 {
        if compare(avail, check(num)) {
            res = append(res, num)
        }
    }
    return res
}

func main() {
    // Example 1:
    // Input: digits = [2,1,3,0]
    // Output: [102,120,130,132,210,230,302,310,312,320]
    // Explanation: All the possible integers that follow the requirements are in the output array. 
    // Notice that there are no odd integers or integers with leading zeros.
    fmt.Println(findEvenNumbers([]int{2,1,3,0})) // [102,120,130,132,210,230,302,310,312,320]
    // Example 2:
    // Input: digits = [2,2,8,8,2]
    // Output: [222,228,282,288,822,828,882]
    // Explanation: The same digit can be used as many times as it appears in digits. 
    // In this example, the digit 8 is used twice each time in 288, 828, and 882. 
    fmt.Println(findEvenNumbers([]int{2,2,8,8,2})) // [222,228,282,288,822,828,882]
    // Example 3:
    // Input: digits = [3,7,5]
    // Output: []
    // Explanation: No even integers can be formed using the given digits.
    fmt.Println(findEvenNumbers([]int{3,7,5})) // []
    fmt.Println(findEvenNumbers([]int{3,7,5,1})) // []
}