add TODO notes

fishercoder1534 · fishercoder1534 · commit f722358bbff5 · 2016-08-05T19:13:58.000-07:00
diff --git a/MEDIUM/src/medium/LengthIncreasingSubsequence.java b/MEDIUM/src/medium/LengthIncreasingSubsequence.java
@@ -21,7 +21,7 @@ Your algorithm should run in O(n2) complexity.
 Credits:
 Special thanks to @pbrother for adding this problem and creating all test cases.*/
 public class LengthIncreasingSubsequence {
-    
+    //TODO: completely understand the following approach and study other good solutions, this is a MUST!!! LIS is a very commonly seen interview question
     public int lengthOfLIS_using_binary_search_from_discuss(int[] nums) {
         /**Java doc for this Arrays.binarySearch method:
          * int java.util.Arrays.binarySearch(int[] a, int fromIndex, int toIndex, int key)
diff --git a/MEDIUM/src/medium/SingleNumberII.java b/MEDIUM/src/medium/SingleNumberII.java
@@ -17,6 +17,8 @@
 */
 public class SingleNumberII {
 
+    //TODO: study its bit manipulation approach, this is a MUST!
+    
     public int singleNumber(int[] nums) {
         Map<Integer, Integer> map = new HashMap();
         for(int i : nums){
diff --git a/MEDIUM/src/medium/SingleNumberIII.java b/MEDIUM/src/medium/SingleNumberIII.java
@@ -18,6 +18,9 @@
 Your algorithm should run in linear runtime complexity. Could you implement it using only constant space complexity?
 */
 public class SingleNumberIII {
+//    TODO: study its bit manipulation way, this is a MUST!
+    
+    
     //Approach 1: normal hashmap
     public int[] singleNumber(int[] nums) {
         Map<Integer, Integer> map = new HashMap();
