firstNonRepeatedElement<T> function

T? firstNonRepeatedElement<T>(List<T> input)

Finds the first non-repeated character in a generic list of elements.

This function counts the frequency of each element in the input list and returns the first element whose frequency is exactly one.

It works with any type T that supports equality comparison.

Returns null if there is no non-repeated element.

Example:

var result = firstNonRepeatedElement<String>(['a', 'a', 'b', 'c', 'd', 'e']);
print(result); // Outputs: b

var nums = [1, 2, 2, 3, 3];
print(firstNonRepeatedElement<int>(nums)); // Outputs: 1

Implementation

T? firstNonRepeatedElement<T>(List<T> input) {
  final Map<T, int> freqMap = {};

  // Count frequency of each element
  for (var element in input) {
    freqMap[element] = (freqMap[element] ?? 0) + 1;
  }

  // Find first element with frequency == 1
  for (var element in input) {
    if (freqMap[element] == 1) {
      return element;
    }
  }

  return null;
}