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; } } }