Question

2094. Finding 3-Digit Even Numbers

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Description

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

Solutions

Solution 1

class Solution:
  def findEvenNumbers(self, digits: List[int]) -> List[int]:
    ans = []
    counter = Counter(digits)
    for i in range(100, 1000, 2):
      t = []
      k = i
      while k:
        t.append(k % 10)
        k //= 10
      cnt = Counter(t)
      if all([counter[i] >= cnt[i] for i in range(10)]):
        ans.append(i)
    return ans

class Solution {
  public int[] findEvenNumbers(int[] digits) {
    int[] counter = count(digits);
    List<Integer> ans = new ArrayList<>();
    for (int i = 100; i < 1000; i += 2) {
      int[] t = new int[3];
      for (int j = 0, k = i; k > 0; ++j) {
        t[j] = k % 10;
        k /= 10;
      }
      int[] cnt = count(t);
      if (check(counter, cnt)) {
        ans.add(i);
      }
    }
    return ans.stream().mapToInt(Integer::valueOf).toArray();
  }

  private boolean check(int[] cnt1, int[] cnt2) {
    for (int i = 0; i < 10; ++i) {
      if (cnt1[i] < cnt2[i]) {
        return false;
      }
    }
    return true;
  }

  private int[] count(int[] nums) {
    int[] counter = new int[10];
    for (int num : nums) {
      ++counter[num];
    }
    return counter;
  }
}

class Solution {
public:
  vector<int> findEvenNumbers(vector<int>& digits) {
    vector<int> counter = count(digits);
    vector<int> ans;
    for (int i = 100; i < 1000; i += 2) {
      vector<int> t(3);
      for (int j = 0, k = i; k > 0; ++j) {
        t[j] = k % 10;
        k /= 10;
      }
      vector<int> cnt = count(t);
      if (check(counter, cnt)) ans.push_back(i);
    }
    return ans;
  }

  vector<int> count(vector<int>& nums) {
    vector<int> counter(10);
    for (int num : nums) ++counter[num];
    return counter;
  }

  bool check(vector<int>& cnt1, vector<int>& cnt2) {
    for (int i = 0; i < 10; ++i)
      if (cnt1[i] < cnt2[i])
        return false;
    return true;
  }
};

func findEvenNumbers(digits []int) []int {
  counter := count(digits)
  var ans []int
  for i := 100; i < 1000; i += 2 {
    t := make([]int, 3)
    k := i
    for j := 0; k > 0; j++ {
      t[j] = k % 10
      k /= 10
    }
    cnt := count(t)
    if check(counter, cnt) {
      ans = append(ans, i)
    }
  }
  return ans
}

func count(nums []int) []int {
  counter := make([]int, 10)
  for _, num := range nums {
    counter[num]++
  }
  return counter
}

func check(cnt1, cnt2 []int) bool {
  for i := 0; i < 10; i++ {
    if cnt1[i] < cnt2[i] {
      return false
    }
  }
  return true
}

function findEvenNumbers(digits: number[]): number[] {
  let record = new Array(10).fill(0);
  for (let digit of digits) {
    record[digit]++;
  }
  let ans = [];
  for (let i = 100; i < 1000; i += 2) {
    if (check(record, String(i))) {
      ans.push(i);
    }
  }
  return ans;
}

function check(target: Array<number>, digits: string): boolean {
  let record = new Array(10).fill(0);
  for (let digit of digits) {
    record[digit]++;
  }

  for (let i = 0; i < 10; i++) {
    if (record[i] > target[i]) return false;
  }
  return true;
}