Skip to content

3438. Find Valid Pair of Adjacent Digits in String 👍

  • Time: $O(n)$
  • Space: $O(10) = O(1)$
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
class Solution {
 public:
  string findValidPair(string s) {
    vector<int> count(10);

    for (const char c : s)
      ++count[c - '0'];

    for (int i = 0; i < s.length() - 1; ++i) {
      const int a = s[i] - '0';
      const int b = s[i + 1] - '0';
      if (a != b && count[a] == a && count[b] == b)
        return s.substr(i, 2);
    }

    return "";
  }
};

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
class Solution {
  public String findValidPair(String s) {
    int[] count = new int[10];

    for (final char c : s.toCharArray())
      ++count[c - '0'];

    for (int i = 0; i < s.length() - 1; ++i) {
      final int a = s.charAt(i) - '0';
      final int b = s.charAt(i + 1) - '0';
      if (a != b && count[a] == a && count[b] == b)
        return s.substring(i, i + 2);
    }

    return "";
  }
}

1
2
3
4
5
6
class Solution:
  def findValidPair(self, s: str) -> str:
    count = collections.Counter(s)
    return next((a + b
                for a, b in itertools.pairwise(s)
                if a != b and count[a] == int(a) and count[b] == int(b)), '')