Update 4.shellSort.md

Author: shouao

4.shellSort.md

@@ -148,20 +148,19 @@ function shellSort($arr)
 ## 7. C++ 代码实现
 
 ```cpp
-void shellSort(vector<int>& nums) {
+void shellSort(vector<int>& arr) {
     int gap = 1;
-    while (gap < (int)nums.size() / 3) {
+    while (gap < (int)arr.size() / 3) {
     	gap = gap * 3 + 1;
     }
     for (; gap >= 1; gap /= 3) {
 	for (int i = 0; i < gap; ++i) {
-	    for (int j = i + gap; j < nums.size(); j += gap) {
-		for (int k = j; k - gap >= 0 && nums[k] < nums[k - gap]; k -= gap) {
-                    swap(nums[k], nums[k - gap]);
+	    for (int j = i + gap; j < arr.size(); j += gap) {
+		for (int k = j; k - gap >= 0 && arr[k] < arr[k - gap]; k -= gap) {
+                    swap(arr[k], arr[k - gap]);
                 }
             }
         }
     }
 }
-
 ```