Added a shaker sort algorithm in dart

Author: Floxyi

Diff for: sort/shaker_sort/dart/shaker_sort.dart

@@ -0,0 +1,48 @@
+void main() {
+  // define a list to be sorted
+  final List<int> unsortedList = [10, 2, 8, 5, 6, 1, 4, 7, 9, 3];
+
+  // define expected result
+  final List<int> expectedList = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+
+  // call the method and save sorted list
+  final List<int> sortedList = shakerSort(unsortedList);
+
+  // test the resolution
+  bool condition1 = sortedList.toSet().difference(expectedList.toSet()).isEmpty;
+  bool condition2 = sortedList.length == expectedList.length;
+  if (condition1 && condition2) {
+    print('Successfully sorted the list!');
+  }
+
+  // print the sorted list
+  print(sortedList);
+}
+
+// define a method that takes the list to sort as input
+List<int> shakerSort(List<int> list) {
+  // the number of steps in the algorithm is only half the length of the input list
+  for (int i = 0; i < list.length / 2; i++) {
+    // first we go through every element in the list starting from the left
+    for (int j = 0; j < list.length - 1; j++) {
+      // if the next element is smaller than the current element, we need to swap them
+      if (list[j] > list[j + 1]) {
+        int temp = list[j];
+        list[j] = list[j + 1];
+        list[j + 1] = temp;
+      }
+    }
+
+    // now each element of the list is run through again from right to left
+    for (int j = list.length - 1; j > 0; j--) {
+      // if the next element is bigger than the current element, we need to swap them
+      if (list[j] < list[j - 1]) {
+        int temp = list[j];
+        list[j] = list[j - 1];
+        list[j - 1] = temp;
+      }
+    }
+  }
+
+  return list;
+}