sample

pad.dart

import 'dart:collection';

void main() {
// Q1
  bool ret = fx(2, 20, 200, 301);
  print(" ${ ret ? "meet" : "not meet" }");
  ret = fx(2, 20, 4, 400);
  print(" ${ ret ? "meet" : "not meet" }");
  print("O(?) step $step");

// Q2
  fx2([]);
  fx2([1, 2, 3, 4, 5]);
  fx2([6, 7, 8, 9, 3, 4, 10, 11, 12]);
  fx2([]);
  print("Q2 O(?) step $step");
}
/*
consider input 2 integer a and b and the goal c and d
implement a function to examinate will (a+b , b) or (a, a+b) will meet c and d
e.g
a = 1 , b = 4, c = 9, d  =4
(1 + 4, 4) = (5, 4)
(4 + 5, 4) = (9, 4)
return true
*/
int step = 0;
bool fx(int a, int b, int c, int d) {
  step++;
  if (a == c && b == d) { // step met 
    return true;
  }
  if (a > c || b > d) {
    return false;
  }
  return fx(a + b, b, c, d) || fx(a, a + b, c, d);
}

/*
consider input array of integer in following sequence
t1 = []
t2 = [1,2,3,4,5]
t3 = [6,7,8,9,10,3,4,11,12]
t4 = []

outputs: 
t2 add [1,2,3,4,5] remove []
t2 add [6,7,8,9,10,11,12] remove [1,2,5]
t2 add [] remove [6,7,8,9,10,11,12]

write a function to output the above result
*/
Set<int> cacheSet = {};

void fx2(List<int> input) {
  Set<int> inputSet = HashSet.from(input);
  Set<int> removeSet = {};
  Set<int> addSet = {};
  removeSet = cacheSet.difference(inputSet);
  print("remove $removeSet");  
  addSet = inputSet.difference(cacheSet);  
  print("add $addSet");
  cacheSet = inputSet;
}