Why do we let the character count go into negative

[Mohammad_Ahmad1]

Why do we let the character count go into negative? and why it doesnt matter for the solution?

e.g. for StringPermutation::findPermutation(“aaaadacb”, “abc”)
charFrequencyMap[‘a’] will go negative and we never correct that becuase check is always on if 0:
if (charFrequencyMap[leftChar] == 0) {

        matched--;  // before putting the character back, decrement the matched count

      }

[Mudasir_Yasin]

The charFrequencyMap[leftChar] is incremented so it will not become negative at any stage.

[Mohammad_Ahmad1]

right char does.
charFrequencyMap[rightChar]–;