The Weekly Challenge 153: Dart solution

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diff --git a/challenge-153/cheok-yin-fung/dart/ch-1.dart b/challenge-153/cheok-yin-fung/dart/ch-1.dart
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+// The Weekly Challenge 153
+// Task 1: Left Factorials
+// Usage: dart ch-1.dart
+
+void main() {
+  const arg = 10;
+  var factorial = [1];
+  for (int i = 1; i <= arg; i++) {
+    factorial.add(factorial[i-1]*i);
+  }
+
+  var leftfactorial = [0];
+
+  for (int i = 1; i <= arg; i++) {
+    leftfactorial.add(leftfactorial[i-1]+factorial[i-1]);
+  }
+  for (int i = 1; i <= arg; i++) {
+    print(leftfactorial[i]);
+  }
+}
diff --git a/challenge-153/cheok-yin-fung/dart/ch-2.dart b/challenge-153/cheok-yin-fung/dart/ch-2.dart
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+++ b/challenge-153/cheok-yin-fung/dart/ch-2.dart
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+// The Weekly Challenge 153
+// Task 2: Factorions
+// Usage: dart ch-2.dart [Positive Integer]
+
+void main(List<String> arguments) {
+// define factorial
+  var factorial = [1];
+  for (int i = 1; i <= 9; i++) {
+    factorial.add(factorial[i-1]*i);
+  }
+
+// convert input into a list of positive integers < 10
+  String mystr = arguments[0];
+  var myint = int.parse(mystr);
+  mystr = myint.toString();   // avoid leading zeros
+  var digits = <int>[];
+  mystr.split("").forEach((item) {
+    digits.add(int.parse(item));
+  });
+
+// sum
+  var sum = 0;
+  digits.forEach((d) {
+    sum += factorial[d];
+  });
+
+// wrap-up
+  print(   myint.toString() + " is a factorion: " 
+         + (sum == myint).toString()               );
+}