myString

myString.java

public class MyString {
  private char[] buffer;
  private MyString next = null;
  private int len = 0;

  public MyString(char[] data) {
    buffer = data.clone();
    len += data.length;
  }

  public int length() {
    return len;
  }

  private int bufferLen() {
    return buffer.length;
  }

  public void concat(char[] data) {
    if (next == null) {
      next = new MyString(data);
    }
    else {
      MyString cur = next;
      while (cur.next != null) {
        cur = cur.next;
      }
      cur.next = new MyString(data);
    }
    len += data.length;
  }

  public String toString() {
    if (next != null) {
      return new String(buffer) + next.toString();
    }
    return new String(buffer);
  }

  public int indexOf(char c) {
    int idx = 0;
    MyString cur = this;
    while (cur != null) {
      for (int i=0; i<cur.bufferLen(); i++, idx++) {
        if (cur.buffer[i] == c) {
          return idx;
        }
      }
      cur = cur.next;
    }
    return -1;
  }

  public int lastIndexOf(char c) {
    int idx = 0;
    int lastIdx = -1;
    MyString cur = this;
    while (cur != null) {
      for (int i=0; i<cur.bufferLen(); i++, idx++) {
        if (cur.buffer[i] == c) {
          lastIdx = idx;
        }
      }
      cur = cur.next;
    }
    return lastIdx;
  }

  private int[] equalUpTo(char[] a, char[] b, int i, int j) {
    while (i < a.length && j < b.length) {
      if (a[i] != b[j]) {
        return null;
      }
      i++;
      j++;
    }
    return new int[]{i, j};
  }

  public boolean equals(MyString other) {
    if (length() != other.length()) {
      return false;
    }
    if (length() == 0) {
      return true;
    }
    MyString cur1 = this;
    MyString cur2 = other;
    int i = 0, j = 0;
    while (cur1 != null && cur2 != null) {
      int[] ret = equalUpTo(cur1.buffer, cur2.buffer, i, j);
      if (ret != null) {
        if (ret[0] >= cur1.bufferLen() && ret[1] >= cur2.bufferLen()) {
          cur1 = cur1.next;
          cur2 = cur2.next;
          i = j = 0;
        } else if (ret[0] >= cur1.bufferLen()) {
          cur1 = cur1.next;
          i = 0;
          j = ret[1];
        } else if (ret[1] >= cur2.bufferLen()) {
          cur2 = cur2.next;
          i = ret[0];
          j = 0;
        }
      } else {
        return false;
      }
    }
    return cur1 == null && cur2 == null;
  }

  public static void main(String[] args) {

  }
}