RotateString

public class StringRotate {
  int count;

  public static void main(String[] argv) {
    StringRotate sr = new StringRotate();
    System.out.println(sr.wordSwap("0123456789", 1));
    System.out.println(sr.wordSwap("012345", 2));
  }

  public String wordSwap(String string, int firstWordLength) {
    count = 0;
    char[] str = string.toCharArray();
    wordSwap(str, 0, str.length, firstWordLength);
    System.out.println(count + " swaps");
    return new String(str);
  }

  // [start, end),
  // first word length: M
  // second word length: N
  public void wordSwap(char[] str, int start, int end, int M) {
    if (end <= start) {
      return;
    }

    final int L = end - start;
    final int N = L - M;

    final int minMN = Math.min(M, N);
    for (int i = 0; i < minMN; ++i) {
      swap(str, start + i, end - minMN + i);
    }

    // only need to recur if M != N
    if (M > N) {
      wordSwap(str, start + N, end, M - N);
    } else if (M < N) {
      wordSwap(str, start, end - M, M);
    }
  }

  private void swap(char[] A, int i, int j) {
    count++;
    char t = A[i];
    A[i] = A[j];
    A[j] = t;
  }
}