Update 4.shellSort.md

Author: Rain120

4.shellSort.md

@@ -22,20 +22,24 @@
 ## 2. JavaScript 代码实现
 
 ```js
-function shellSort(arr) {
+/**
+ * arr:  排序数组
+ *  gapLen: 排序增量
+ **/
+function shellSort(arr, gapLen) {
     var len = arr.length,
         temp,
         gap = 1;
-    while(gap < len/3) {          //动态定义间隔序列
-        gap =gap*3+1;
+    while(gap < len / gapLen) {          //动态定义间隔序列
+        gap = gap * gapLen + 1;
     }
-    for (gap; gap > 0; gap = Math.floor(gap/3)) {
+    for (gap; gap > 0; gap = Math.floor(gap / gapLen)) {
         for (var i = gap; i < len; i++) {
             temp = arr[i];
-            for (var j = i-gap; j >= 0 && arr[j] > temp; j-=gap) {
-                arr[j+gap] = arr[j];
+            for (var j = i - gap; j >= 0 && arr[j] > temp; j -= gap) {
+                arr[j + gap] = arr[j];
             }
-            arr[j+gap] = temp;
+            arr[j + gap] = temp;
         }
     }
     return arr;