main.dart

void main() {
  isProperlyNested(String str) {
    var splittedString = str.split("");
    List outputs = [];

    for (var i = 0; i < str.length; i++) {
      var currentVal = str[i];

      if (currentVal == '{' || currentVal == '(' || currentVal == '[') {
        outputs.add(currentVal);
      } else if (currentVal == '}' || currentVal == ')' || currentVal == ']') {
        var t = outputs.removeLast() + currentVal;
        if (t != "{}" && t != "()" && t != "[]") return 'Not properly nested';
      } else {
        return 'Not properly nested';
      }
    }

    if (outputs.isNotEmpty) {
      return 'Not properly nested';
    } else {
      return 'String is properly nested';
    }
  }

  print(isProperlyNested("(){){("));
  print(isProperlyNested("({[]})")); 
}