Maximize Number of Subsequences in a String LeetCode solution in C++

1
class Solution {
2
 public:
3
  long long maximumSubsequenceCount(string text, string pattern) {
4
    // support variables
5
    int len = text.size();
6
    long long res = 0, aCount = 0, bCount = 0;
7
    char a = pattern[0], b = pattern[1];
8
    // getting the frequencies
9
    for (char c : text) {
10
      if (c == a)
11
        aCount++;
12
      else if (c == b)
13
        bCount++;
14
    }
15
    // edge case: a == b
16
    if (a == b) return aCount++ * aCount / 2;
17
    // adding our extra character to maximise the occurrences
18
    if (aCount < bCount)
19
      res += bCount;
20
    else
21
      bCount++;
22
    // computing the occurrences
23
    for (char c : text) {
24
      // first case: spotting the first element of a sequence
25
      if (c == a) {
26
        res += bCount;
27
      }
28
      // second case: we found an ending sequence
29
      else if (c == b)
30
        bCount--;
31
      // all the rest: we do nothing
32
    }
33
    return res;
34
  }
35
};