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public class Q2_reverseString {
    // Method 1: built in StringBuffer function
	public static void reverseString(String str) {

		for (String part : str.split(" ")) {
			System.out.print(new StringBuffer(part).reverse().toString());
			System.out.print(" ");
		}
	}

	public static String reverse(String str_words) {
		char[] c_array = str_words.toCharArray();
		int pos_start = 0;
		int pos_end;
		char c, c_tmp;
		int i, j, rev_length;
		for (i = 0; i < c_array.length; i++) {
			c = c_array[i];
			if (c == ' ' || c == '\n') {
				if (pos_start != i) {
					pos_end = i - 1;
					rev_length = (i - pos_start) / 2;
					for (j = 0; j < rev_length; j++) {
						c_tmp = c_array[pos_start + j];
						c_array[pos_start + j] = c_array[pos_end - j];
						c_array[pos_end - j] = c_tmp;
					}
				}
				pos_start = i + 1;
			}
		}
		// redundant, if only java had '\0' @ end of string
		if (pos_start != i) {
			pos_end = i - 1;
			rev_length = (i - pos_start) / 2;
			for (j = 0; j < rev_length; j++) {
				c_tmp = c_array[pos_start + j];
				c_array[pos_start + j] = c_array[pos_end - j];
				c_array[pos_end - j] = c_tmp;
			}
		}
		return new String(c_array);
	}

	public static String reverse(String in, String out) {
		return (in.isEmpty()) ? out : (in.charAt(0) == ' ') ? out + ' '
				+ reverse(in.substring(1), "") : reverse(in.substring(1),
				in.charAt(0) + out);
	}

	public static String reverseSimple(String s) {
        if (s == null || s.length() == 0)
    		return null;
		int length = s.length(), last = length - 1;
		char[] chars = s.toCharArray();
		for (int i = 0; i < length / 2; i++) {
			char c = chars[i];
			chars[i] = chars[last - i];
			chars[last - i] = c;
		}
		return new String(chars);
	}
}