001
002
003
004
005
006
007
008
009
010
011
012
013
014
015
016
017
018
019
020
021
022
023
024
025
026
027
028
029
030
031
032
033
034
035
036
037
038
039
040
041
042
043
044
045
046
047
048
049
050
051
052
053
054
055
056
057
058
059
060
061
062
063
064
065
066
067
068
069
070
071
072
073
074
075
076
077
078
079
080
081
082
083
084
085
086
087
088
089
090
091
092
093
094
095
096
097
098
099
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
package algs13;
import stdlib.*;
import java.text.DecimalFormat;
import java.util.NoSuchElementException;

/**
 * This is a skeleton file for your homework.
 * Complete the functions below. 
 * You may also edit the function "main" to test your code.
 * 
 * You should not use any loops or recursions, except in "delete"
 * Delete may use one loop or recursive helper.
 *
 * You must not add fields or static variables.
 * As always, you must not change the declaration of any method.
 * Do not change any of the methods I have provided, such as "toString" and "check".
 */

public class MyDeque {
  Node first = null;
  Node last = null;
  int N = 0;

  static class Node {
    public Node (double item) { this.item = item; }
    public double item;
    public Node next;
    public Node prev;
  }

  public MyDeque ()         { };
  public boolean isEmpty () { return N == 0; }
  public int size ()        { return N; }

  public void pushLeft (double item) {
    // TODO
  }

  public double popLeft () {
    if (N == 0) throw new NoSuchElementException ();
    return StdRandom.uniform ();
    // TODO
  }

  public void pushRight (double item) {
    // TODO
  }
  
  public double popRight () {
    if (N == 0) throw new NoSuchElementException ();
    return StdRandom.uniform ();
    // TODO
  }

  /* The concat method should take the Nodes from "that" and add them to "this"
   * After execution, "that" should be empty.
   * See the tests in the main program.
   *
   * Do not use a loop or a recursive definition.
   * This method can declare Node variables, but may not create new node objects (using "new").
   * Therefore the method should not call pushLeft or pushRight (which use create new objects).
   */
  public void concat (MyDeque that) {
    // TODO
  }

  /* Delete should delete and return the kth element from the left (where k is between 0 and N-1).
   * See the tests in the main program.
   *
   * You may use a loop or a recursive definition here.
   * This method can declare Node variables, but may not create new node objects (using "new").
   * Therefore the method should not call pushLeft or pushRight (which use create new objects).
   */
  public double delete (int k) {
    if (k < 0 || k >= N) throw new IllegalArgumentException ();
    return StdRandom.uniform ();
    // TODO 
  }


  public static void main (String args[]) {
    // TODO: Uncomment these lines to use the visual debugger
    // Note, however, that this will substantially slow things down
    // So you should leave these commented unless you are using the debugger
    //
    // Trace.drawStepsOfMethod ("main");
    // Trace.drawStepsOfMethod ("pushLeft");
    // Trace.run ();

    // Here are some tests to get you started.
    // You can edit this all you like.
    MyDeque d1, d2, d3;
    double k;

    ////////////////////////////////////////////////////////////////////
    // push/pop tests
    ////////////////////////////////////////////////////////////////////
    d1 = new MyDeque ();
    d1.pushLeft (11);
    check ("left1", d1, "[ 11 ]");
    d1.pushLeft (12);
    check ("left2", d1, "[ 12 11 ]");
    d1.pushLeft (13);
    check ("left3", d1, "[ 13 12 11 ]");
    k = d1.popLeft ();
    check ("left4", d1, "[ 12 11 ]", k, 13);
    k = d1.popLeft ();
    check ("left5", d1, "[ 11 ]", k, 12);
    k = d1.popLeft ();
    check ("left6", d1, "[ ]", k, 11);

    d1 = new MyDeque ();
    d1.pushRight (11);
    check ("right1", d1, "[ 11 ]");
    d1.pushRight (12);
    check ("right2", d1, "[ 11 12 ]");
    d1.pushRight (13);
    check ("right3", d1, "[ 11 12 13 ]");
    k = d1.popRight ();
    check ("right4", d1, "[ 11 12 ]", k, 13);
    k = d1.popRight ();
    check ("right5", d1, "[ 11 ]", k, 12);
    k = d1.popRight ();
    check ("right6", d1, "[ ]", k, 11);

    d1 = new MyDeque ();
    d1.pushLeft (11);
    check ("left/right1", d1, "[ 11 ]");
    d1.pushRight (21);
    check ("left/right2", d1, "[ 11 21 ]");
    d1.pushLeft (12);
    check ("left/right3", d1, "[ 12 11 21 ]");
    d1.pushRight (22);
    check ("left/right4", d1, "[ 12 11 21 22 ]");
    k = d1.popLeft ();
    check ("left/right5", d1, "[ 11 21 22 ]", k, 12);
    k = d1.popLeft ();
    check ("left/right6", d1, "[ 21 22 ]", k, 11);
    k = d1.popLeft ();
    check ("left/right7", d1, "[ 22 ]", k, 21);
    k = d1.popLeft ();
    check ("left/right8", d1, "[ ]", k, 22);

    d1 = new MyDeque ();
    d1.pushLeft (11);
    check ("left/right10", d1, "[ 11 ]");
    d1.pushRight (21);
    check ("left/right11", d1, "[ 11 21 ]");
    d1.pushLeft (12);
    check ("left/right12", d1, "[ 12 11 21 ]");
    d1.pushRight (22);
    check ("left/right13", d1, "[ 12 11 21 22 ]");
    k = d1.popRight ();
    check ("left/right14", d1, "[ 12 11 21 ]", k, 22);
    k = d1.popRight ();
    check ("left/right15", d1, "[ 12 11 ]", k, 21);
    k = d1.popRight ();
    check ("left/right16", d1, "[ 12 ]", k, 11);
    k = d1.popRight ();
    check ("left/right17", d1, "[ ]", k, 12);

    ////////////////////////////////////////////////////////////////////
    //  test exceptions
    ////////////////////////////////////////////////////////////////////
    try {
      d1.popLeft ();
      showError ("Expected exception1");
    } catch (NoSuchElementException e) {}
    try {
      d1.popRight ();
      showError ("Expected exception2");
    } catch (NoSuchElementException e) {}

    ////////////////////////////////////////////////////////////////////
    // concat tests (and more push/pop tests)
    ////////////////////////////////////////////////////////////////////
    d1 = new MyDeque ();
    d1.concat (new MyDeque ());
    check ("concat1", d1, "[ ]");
    d1.pushLeft (11);
    d1.concat (new MyDeque ());
    check ("concat2", d1, "[ 11 ]");

    d1 = new MyDeque ();
    d2 = new MyDeque ();
    d2.pushLeft (11);
    d1.concat (d2);
    check ("concat3a", d1, "[ 11 ]");
    check ("concat3b", d2, "[ ]");

    d1 = new MyDeque ();
    d2 = new MyDeque ();
    d1.pushLeft (11);
    d1.pushLeft (12);
    d2.pushLeft (21);
    d2.pushLeft (22);
    d1.concat (d2);
    check ("concat4a", d1, "[ 12 11 22 21 ]");
    check ("concat4b", d2, "[ ]");
    d2.concat (d1);
    check ("concat5a", d2, "[ 12 11 22 21 ]");
    check ("concat5b", d1, "[ ]");

    d1 = new MyDeque ();
    for (int i = 10; i < 13; i++) { d1.pushLeft (i); checkInvariants ("left1", d1); }
    for (int i = 20; i < 23; i++) { d1.pushRight (i); checkInvariants ("right2", d1); }
    check ("concat6", d1, "[ 12 11 10 20 21 22 ]");
    d2 = new MyDeque ();
    d1.concat (d2);
    check ("concat7a", d1, "[ 12 11 10 20 21 22 ]");
    check ("concat7b", d2, "[ ]");

    for (int i = 30; i < 33; i++) { d2.pushLeft (i); checkInvariants ("left3", d2); }
    for (int i = 40; i < 43; i++) { d2.pushRight (i); checkInvariants ("right4", d2); }
    check ("concat9", d2, "[ 32 31 30 40 41 42 ]");

    d3 = new MyDeque ();
    d2.concat (d3);
    check ("concat10", d2, "[ 32 31 30 40 41 42 ]");
    check ("concat11", d3, "[ ]");

    d1.concat (d2);
    check ("concat12", d1, "[ 12 11 10 20 21 22 32 31 30 40 41 42 ]");
    check ("concat13", d2, "[ ]");
    for (int i = 0; i < 12; i++) { d1.popLeft (); checkInvariants ("left5", d1); }
    ////////////////////////////////////////////////////////////////////
    // delete tests
    ////////////////////////////////////////////////////////////////////
    d1 = new MyDeque ();
    d1.pushLeft (11);
    k = d1.delete (0);
    check ("delete1", d1, "[ ]", k, 11);
    for (int i = 10; i < 20; i++) { d1.pushRight (i); checkInvariants ("right6", d1); }
    k = d1.delete (0);
    check ("delete2", d1, "[ 11 12 13 14 15 16 17 18 19 ]", k, 10);
    k = d1.delete (8);
    check ("delete3", d1, "[ 11 12 13 14 15 16 17 18 ]", k, 19);
    k = d1.delete (4);
    check ("delete4", d1, "[ 11 12 13 14 16 17 18 ]", k, 15);
    k = d1.delete (3);
    check ("delete5", d1, "[ 11 12 13 16 17 18 ]", k, 14);
    k = d1.delete (0);
    check ("delete6", d1, "[ 12 13 16 17 18 ]", k, 11);
    k = d1.delete (4);
    check ("delete7", d1, "[ 12 13 16 17 ]", k, 18);
    k = d1.delete (3);
    check ("delete8", d1, "[ 12 13 16 ]", k, 17);
    k = d1.delete (1);
    check ("delete9", d1, "[ 12 16 ]", k, 13);
    k = d1.delete (1);
    check ("delete10", d1, "[ 12 ]", k, 16);
    k = d1.delete (0);
    check ("delete10", d1, "[ ]", k, 12);
    
    ////////////////////////////////////////////////////////////////////
    // More push/pop
    ////////////////////////////////////////////////////////////////////
    d1 = new MyDeque();
    d1.pushRight(21);
    check("left/right20", d1, "[ 21 ]");
    d1.pushLeft(11);
    check("left/right21", d1, "[ 11 21 ]");
    k = d1.popLeft();
    check("left/right22", d1, "[ 21 ]", k, 11);
    d1.pushRight(22);
    check("left/right23", d1, "[ 21 22 ]");

    d1 = new MyDeque();
    d1.pushRight(21);
    check("left/right30", d1, "[ 21 ]");
    d1.pushRight(22);
    check("left/right31", d1, "[ 21 22 ]");
    d1.pushLeft(11);
    check("left/right32", d1, "[ 11 21 22 ]");
    k = d1.popLeft();
    check("left/right33", d1, "[ 21 22 ]", k, 11);
    k = d1.popLeft();
    check("left/right34", d1, "[ 22 ]", k, 21);
    d1.pushLeft(12);
    check("left/right35", d1, "[ 12 22 ]");
    StdOut.println ("Finished tests");
  }
  
  public MyDeque (String s) {
    String[] nums = s.split (" ");
    for (int i = nums.length-1; i >= 0; i--) {
      try { 
        pushLeft (Double.parseDouble (nums[i]));      
      } catch (NumberFormatException e) { }
    }
  }
  public String toString () { 
    DecimalFormat format = new DecimalFormat ("#.###");
    StringBuilder result = new StringBuilder ("[ ");
    for (Node x = first; x != null; x = x.next) {
      result.append (format.format (x.item));
      result.append (" ");
    }
    result.append ("]");
    return result.toString ();
  }


  private static void checkInvariants (String message, MyDeque that) {
    int N = that.N;
    MyDeque.Node first = that.first;
    MyDeque.Node last = that.last;

    if (N < 0) throw new Error ();
    if (N == 0) {
      if (first != null) {
        showError (String.format ("%s: N==0, Expected first == null.", message));
      }
      if (last != null) {
        showError (String.format ("%s: N==0, Expected last == null.", message));
      }
    } else {
      if (first == null) {
        showError (String.format ("%s: N!=0, Expected first != null.", message));
      }
      if (last == null) {
        showError (String.format ("%s: N!=0, Expected last != null.", message));
      }
    }
    if (N > 0) {
      MyDeque.Node prev = null;
      MyDeque.Node current = first;
      for (int i = 0; i < N; i++) {
        if (current == null) {
          showError (String.format ("%s: N==%d, Expected %d next nodes, but got less.", message, N, N));
          return;
        }
        if (current.prev != prev) { 
          showError (String.format ("%s: i=%d, Broken prev link.", message, i));
          return;
        }
        prev = current;
        current = current.next;
      }
      if (current != null) {
        showError (String.format ("%s: N==%d, Expected %d next nodes, but got more.", message, N, N));
        return;
      }
      MyDeque.Node next = null;
      current = last;
      for (int i = 0; i < N; i++) {
        if (current == null) {
          showError (String.format ("%s: N==%d, Expected %d prev nodes, but got less.", message, N, N));
          return;
        }
        if (current.next != next) {
          showError (String.format ("%s: i=%d, Broken next link.", message, i));
          return;
        }
        next = current;
        current = current.prev;
      }
      if (current != null) {
        showError (String.format ("%s: N==%d, Expected %d prev nodes, but got more.", message, N, N));
        return;
      }
    }
  }
  private static void check (String message, MyDeque actual, String expected) {
    checkInvariants (message, actual);
    if (expected != null) {
      if (!expected.equals (actual.toString ())) {
        showError ("Expected \"" + expected + "\", got \"" + actual + "\"");
        return;
      }
    }
  }
  private static void check (String message, MyDeque actual, String expected, double dActual, double dExpected) {
    if (dExpected != dActual) {
      showError ("Expected \"" + dExpected + "\", got \"" + dActual + "\"");
      return;
    }
    check (message, actual, expected);
  }

  private static void showError (String message) {
    Trace.draw ();
    StdOut.println (message);
    throw new Error (); // stops execution
  }
}