Update 5.mergeSort.md

Author: shouao

5.mergeSort.md

@@ -247,8 +247,8 @@ void merge(vector<int>& nums, int l, int mid, int r) {
     }
     copy(tempary.begin(), tempary.begin() + index, nums.begin() + l);
 }
-void mergeSort(vector<int>& nums, int l, int r) {// range is [l, r), so if there is a 0-index array arr whose length is n, "mergeSort(arr, 0, n)" should be called
-    if (r - l <= 1) {
+void mergeSort(vector<int>& nums, int l, int r) {// sort the range [l, r), so if there is a 0-index array arr whose length is n
+    if (r - l <= 1) {                            //and you want sort the whole array, "mergeSort(arr, 0, n)" should be called
         return;
     }
     int mid = (l + r) / 2;