Misht Community #1

week1_rob.java

import static org.junit.Assert.assertEquals;

import java.util.*;
import java.lang.*;
import java.io.*;

/* 
"Given an input string s, reverse words in a string." 
Do this in-place without allocating an extra space. 
The input string doesn't contain any leading or trailing 
spaces and all words are separated by a single space.

For example, given string "the weather is cold today", 
return "today cold is weather the". 

O(n) cpu, O(n) space - reverse the entire string first, 
then reverse each word

@author rcmccartney
*/
class Ideone {
	
	public static String doIt(String toReverse) {
		StringBuilder stb = new StringBuilder(toReverse);
		// could just use stringbuilder reverse, but for completeness..
		reverseStr(stb, 0, stb.length()-1);
		int start = 0, end = 0;
		while (start < stb.length()) {
			while (end < stb.length() && stb.charAt(end) != ' ') {
				end++;
			}
			reverseStr(stb, start, end-1);
			start = ++end;  // skip whitespace and start next word 
		}
		return stb.toString();
	}
	
	public static void reverseStr(StringBuilder stb, int start, int end) {
		char temp;
		while (start < end) {
			temp = stb.charAt(end);
			stb.setCharAt(end--, stb.charAt(start));
			stb.setCharAt(start++, temp);
		}
	}
	
	public static void main (String[] args) throws java.lang.Exception {
		// assertEquals seems broken on ideone.com, will just print them
		System.out.println("1. " + doIt("the weather is cold today"));
		System.out.println("2. " + doIt("oneword"));
		System.out.println("3. " + doIt("A longer string periods may mess it up."));
		System.out.println("4. " + doIt(""));
	}
}