ReverseWordsII.java

package string;

/**
 * Created by gouthamvidyapradhan on 21/03/2017. Given an input string, reverse the string word by
 * word. A word is defined as a sequence of non-space characters.
 *
 * <p>The input string does not contain leading or trailing spaces and the words are always
 * separated by a single space.
 *
 * <p>For example, Given s = "the sky is blue", return "blue is sky the".
 *
 * <p>Could you do it in-place without allocating extra space?
 */
public class ReverseWordsII {
  /**
   * Main method
   *
   * @param args
   * @throws Exception
   */
  public static void main(String[] args) throws Exception {
    char[] c = {'t', 'h', 'e', ' ', 's', 'k', 'y', ' ', 'i', 's', ' ', 'b', 'l', 'u', 'e'};
    new ReverseWordsII().reverseWords(c);
    for (char i : c) System.out.print(i);
  }

  public void reverseWords(char[] s) {
    for (int i = 0, j = s.length - 1; i < j; i++, j--) {
      char temp = s[i];
      s[i] = s[j];
      s[j] = temp;
    }
    for (int i = 0, j = 0, l = s.length; i < l; ) {
      if (s[i] == ' ') {
        if (s[i - 1] == ' ') {
          j = i;
          i++;
          j++;
        } else {
          i = i - 1;
          for (int p = j, q = i; p < q; p++, q--) {
            char temp = s[p];
            s[p] = s[q];
            s[q] = temp;
          }
          i = i + 1;
          j = i;
          i++;
          j++;
        }
      } else if (i == l - 1) {
        for (int p = j, q = i; p < q; p++, q--) {
          char temp = s[p];
          s[p] = s[q];
          s[q] = temp;
        }
        j = i;
        i++;
        j++;
      } else {
        i++;
      }
    }
  }
}