LeetCode-Reverse Words in a String[AC源码]

 package com.lw.leet1;

 import java.util.Stack;

 /**
  * @ClassName:Solution
  * @Description:
  *         Reverse Words in a String
  *         Total Accepted: 26194 Total Submissions: 187094 My Submissions
  *         Given an input string, reverse the string word by word.
  *
  *         For example
  *             Given s = "the sky is blue"
  *             return "blue is sky the".
  *
  *         Clarification:
  *             What constitutes a word?
  *             A sequence of non-space characters constitutes a word.
  *         Could the input string contain leading or trailing spaces?
  *             Yes. However, your reversed string should not contain leading or trailing spaces.
  *         How about multiple spaces between two words?
  *             Reduce them to a single space in the reversed string.
  *
  * @Author LiuWei
  * @Date 2014年8月15日下午7:48:48
  * @Mail nashiyue1314@163.com
  */
 public class Solution {

     public String reverseWords(String word){
         Stack<String> sstack = new Stack<String>();
         int flag = 0;
         for(int i= 0; i<word.length(); i++){
             while(i<word.length() && word.charAt(i)==' '){
                 i++;
             }
             flag = i;
             while(i<word.length() && word.charAt(i)!=' '){
                 i++;
             }
             if(flag != i){
                 sstack.push(word.substring(flag, i));
             }
         }
         String res = "";
         while(!sstack.isEmpty()){
             res += sstack.pop()+" ";
         }
 //        The input string which is made up of space
         if(res.length()==0){
             return "";
         }
         return res.substring(0, res.length()-1);
     }

     public String reverseWords2(String word){
         String res ="";
         int flag = 0;
         for(int i= 0; i<word.length(); i++){
             while(i<word.length() && word.charAt(i)==' '){
                 i++;
             }
             flag = i;
             while(i<word.length() && word.charAt(i)!=' '){
                 i++;
             }
             if(flag != i){
                 res = word.substring(flag, i)+" "+res;
             }
         }
 //        The input string which is made up of space
         if(res.length()==0){
             return "";
         }
         return res.substring(0, res.length()-1);
     }

     public static void main(String[] args){
         Solution s = new Solution();
         System.out.println(s.reverseWords2("   hello world    "));
     }
 }