add comment for 88

Author: fishercoder1534

Diff for: src/main/java/com/fishercoder/solutions/_88.java

@@ -3,6 +3,9 @@
 public class _88 {
 
     public static class Solution1 {
+        /**
+         * The key to reach this optimal solution is: start from the right side instead of the left.
+         */
         public void merge(int[] nums1, int m, int[] nums2, int n) {
             int i = m - 1;
             int j = n - 1;