Merge pull request larissalages#258 from ALaurinne/3-merge-sort

Add Merge Sort in Dart.

Author: larissalages

classical_algorithms/dart/MergeSort.dart

@@ -0,0 +1,47 @@
+void merge(List list, int leftIndex, int middleIndex, int rightIndex) {
+  int leftSize = middleIndex - leftIndex + 1;
+  int rightSize = rightIndex - middleIndex;
+
+  List leftList = List(leftSize);
+  List rightList = List(rightSize);
+
+  for (int i = 0; i < leftSize; i++) leftList[i] = list[leftIndex + i];
+  for (int j = 0; j < rightSize; j++) rightList[j] = list[middleIndex + j + 1];
+
+  int i = 0, j = 0;
+  int k = leftIndex;
+
+  while (i < leftSize && j < rightSize) {
+    if (leftList[i] <= rightList[j]) {
+      list[k] = leftList[i];
+      i++;
+    } else {
+      list[k] = rightList[j];
+      j++;
+    }
+    k++;
+  }
+
+  while (i < leftSize) {
+    list[k] = leftList[i];
+    i++;
+    k++;
+  }
+
+  while (j < rightSize) {
+    list[k] = rightList[j];
+    j++;
+    k++;
+  }
+}
+
+void mergeSort(List list, int leftIndex, int rightIndex) {
+  if (leftIndex < rightIndex) {
+    int middleIndex = (rightIndex + leftIndex) ~/ 2;
+
+    mergeSort(list, leftIndex, middleIndex);
+    mergeSort(list, middleIndex + 1, rightIndex);
+
+    merge(list, leftIndex, middleIndex, rightIndex);
+  }
+}

readme.md

@@ -37,6 +37,7 @@ Code | Test
 [Bubble Sort](https://github.com/larissalages/code_problems/blob/master/classical_algorithms/dart/BubbleSort.dart) | Missing tests
 [Quick Sort](https://github.com/larissalages/code_problems/blob/master/classical_algorithms/dart/QuickSort.dart) | Missing tests
 [Binary Sort](https://github.com/larissalages/code_problems/blob/master/classical_algorithms/dart/BinarySort.dart) | Missing tests
+[Merge Sort](https://github.com/larissalages/code_problems/blob/master/classical_algorithms/java/MergeSort.dart) | Missing tests
 
 ### C++
 Code | Test