LeetCode-Reverse Words in a String II

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?

Analysis:

We reverse the whole string first, and then reverse each word again.

Solution:

public class Solution {
public void reverseWords(char[] s) {
reverse(s,0,s.length-1);

int p1=0,p2=0;
while (p1 < s.length){
p2 = p1;
while (p2 < s.length && s[p2]!=' '){
p2++;
}
reverse(s,p1,p2-1);
p1 = p2+1;
}
}

public void reverse(char[] s, int start, int end){
while (start < end){
char temp = s[start];
s[start++] = s[end];
s[end--] = temp;
}
}
}