Merge pull request #25 from fluttermiddlepodcast/2544_Alternating_Digit_Sum

added "2544. Alternating Digit Sum"

Author: fluttermiddlepodcast

README.md

@@ -21,6 +21,7 @@ Solutions from [LeetCode](https://leetcode.com) on Dart.
 | 2239. Find Closest Number to Zero       | [Link](https://leetcode.com/problems/find-closest-number-to-zero/)         | [Link](./lib/easy/find_closest_number_to_zero.dart)         |
 | 2481. Minimum Cuts to Divide a Circle   | [Link](https://leetcode.com/problems/minimum-cuts-to-divide-a-circle/)     | [Link](./lib/easy/minimum_cuts_to_divide_a_circle.dart)     |
 | 2490. Circular Sentence                 | [Link](https://leetcode.com/problems/circular-sentence/)                   | [Link](./lib/easy/circular_sentence.dart)                   |
+| 2544. Alternating Digit Sum             | [Link](https://leetcode.com/problems/alternating-digit-sum/)               | [Link](./lib/easy/alternating_digit_sum.dart)               |
 
 ## Medium
 

lib/easy/alternating_digit_sum.dart

@@ -0,0 +1,12 @@
+class Solution {
+  int alternateDigitSum(int n) {
+    int result = 0;
+    int factor = 1;
+    final str = n.toString();
+    for (int i = 0; i < str.length; i++) {
+      result += int.parse(str[i]) * factor;
+      factor *= -1;
+    }
+    return result;
+  }
+}

test/easy/alternating_digit_sum_test.dart

@@ -0,0 +1,14 @@
+import 'package:leetcode_dart/easy/alternating_digit_sum.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group(
+    'Example tests',
+    () {
+      final ads = Solution();
+      test('4', () => expect(4, ads.alternateDigitSum(521)));
+      test('1', () => expect(1, ads.alternateDigitSum(111)));
+      test('0', () => expect(0, ads.alternateDigitSum(886996)));
+    },
+  );
+}