packagemedium;

publicclassReverseWordsinaString {

publicStringreverseWords(Strings) {

if(!s.contains(" "))returns;//for cases like this: "a"

if(s.matches(" *"))return"";//for cases like this: " "

String[]words =s.split(" ");

StringBuildersb =newStringBuilder();

for(inti =words.length-1;i >=0;i--){

if(!words[i].equals("") && !words[i].equals(" ")){

sb.append(words[i]);

sb.append(" ");

}

}

sb.deleteCharAt(sb.length()-1);

returnsb.toString();

}

}

|165|[Compare Version Numbers](https://leetcode.com/problems/compare-version-numbers/)|[Solution](../../blob/master/EASY/src/easy/CompareVersionNumbers.java)| O(n)|O(1)| Easy|

|162|[Find Peak Element](https://leetcode.com/problems/find-peak-element/)|[Solution](../../blob/master/MEDIUM/src/medium/FindPeakElement.java)| O(1)|O(logn)/O(n)| Binary Search|

|155|[Min Stack](https://leetcode.com/problems/min-stack/)|[Solution](../../blob/master/EASY/src/easy/MinStack.java)| O(1)|O(n) | Easy| Stack

|151|[Reverse Words in a String](https://leetcode.com/problems/reverse-words-in-a-string/)|[Solution](../../blob/master/MEDIUM/src/medium/ReverseWordsinaString.java)| O(n)|O(n)| Medium|

|140|[Word Break II](https://leetcode.com/problems/word-break-ii/)|[Solution](../../blob/master/HARD/src/hard/WordBreakII.java)| ? |O(n^2) | Hard| Backtracking/DFS

|139|[Word Break](https://leetcode.com/problems/word-break/)|[Solution](../../blob/master/MEDIUM/src/medium/WordBreak.java)| O(n^2)|O(n) | Medium| DP

|133|[Clone Graph](https://leetcode.com/problems/clone-graph/)|[Solution](../../blob/master/MEDIUM/src/medium/CloneGraph.java)| O(n)|O(n) | Medium| HashMap, BFS