Problem

Reverse Words in a String II

Given an input string , reverse the string word by word.

Example

Input: ["t","h","e"," ","s","k","y"," ","i","s"," ","b","l","u","e"]

Output: ["b","l","u","e"," ","i","s"," ","s","k","y"," ","t","h","e"]

Note

A word is defined as a sequence of non-space characters.

The input string does not contain leading or trailing spaces.The words are always separated by a single space.Follow up: Could you do it in-place without allocating extra space?

Solution

class Solution {    public void reverseWords(char[] str) {        int start = 0, end = str.length-1;        //reverse all chars        reverse(str, start, end);        for (int i = 0; i < str.length; i++) {            //reverse all words back, except for the last one            if (str[i] == ' ') {                reverse(str, start, i-1);                start = i+1;            }        }        //reverse the last word back        reverse(str, start, end);    }    private void reverse(char[] str, int i, int j) {        while (i < j) {            char temp = str[i];            str[i] = str[j];            str[j] = temp;            i++;            j--;        }    }}