Medium 186题 Reverse Words in a String II

Question:

Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters.

The input string does not contain leading or trailing spaces and the words are always separated by a single space.

For example,

Given s = "

the sky is blue

",

return "

blue is sky the

".

Could you do it in-place without allocating extra space?

Solution:

public class Solution {
public void reverseWords(char[] s) {

//1.reverse the whole word
reverse(s,0,s.length-1);
//2.reverse each word
int start = 0;
for(int i=0;i<=s.length-1;i++){
if(s[i]==' '){
reverse(s,start,i-1);
start=i+1;
}
}
//0. if we have only one word
reverse(s,start,s.length-1);
}
public void reverse(char[] s,int start, int end){
while(start<end){
char tmp=s[start];
s[start]=s[end];
s[end]=tmp;
start++;
end--;
}
}
}