本文比第一篇，采用了类实现。增加了运算符重载等功能。本来有序数组是不能修改某个位置的值的，因为这样会打破数组的有序性；但为了演示，保留了修改的方法，但为此增加了排序。
1 import 'dart:math' show Random;
2
3 final _rnd = Random();
4 final _seed = 100;
5
6 class OrderedArray {
7 List<int> _array;
8 int _realLength;
9
10 OrderedArray(int capacity) {
11 _array = List<int>(capacity);
12 _realLength = 0;
13 }
14
15 int get capacity => _array.length;
16 int get length => _realLength;
17
18 void fill(double percent) {
19 for (var i = 0; i < capacity * percent; i++) {
20 insert(_rnd.nextInt(_seed));
21 }
22 }
23
24 bool insert(int v) {
25 if (_realLength == capacity) {
26 return false;
27 } else {
28 if (_realLength == 0) {
29 _array[0] = v;
30 } else {
31 int i;
32 for (i = 0; i < _realLength; i++) {
33 if (_array[i] >= v) break;
34 }
35 for (var j = _realLength; j > i; j--) {
36 _array[j] = _array[j - 1];
37 }
38 _array[i] = v;
39 }
40
41 _realLength++;
42 return true;
43 }
44 }
45
46 int find(int key) {
47 if (_realLength == 0) {
48 return -1;
49 }
50
51 if (key < _array[0] || key > _array[_realLength - 1]) {
52 return -1;
53 }
54
55 int lower = 0, upper = _realLength - 1, mid;
56 while (lower <= upper) {
57 mid = (lower + upper) ~/ 2;
58 if (_array[mid] == key) {
59 return mid;
60 } else if (_array[mid] > key) {
61 upper = mid - 1;
62 } else {
63 lower = mid + 1;
64 }
65 }
66 return -1;
67 }
68
69 // Attention! after modifed the array is maybe not ordered ever.
70 bool modify(int pos, int newValue) {
71 if (pos < 0 || pos > _realLength - 1) {
72 return false;
73 } else {
74 _array[pos] = newValue;
75 // sort(0, _realLength - 1);
76 return true;
77 }
78 }
79
80 bool delete(int key) {
81 var pos = find(key);
82 if (pos < 0) {
83 return false;
84 } else {
85 for (var i = pos; i < _realLength - 1; i++) {
86 _array[i] = _array[i + 1];
87 }
88 _realLength--;
89 return true;
90 }
91 }
92
93 int operator [](int pos) {
94 if (pos < 0 || pos > _realLength - 1) {
95 return null;
96 } else {
97 return _array[pos];
98 }
99 }
100
101 // the below is equal to modify, but don't have return type;
102 void operator []=(int pos, int newValue) {
103 if (pos >= 0 && pos < _realLength) {
104 _array[pos] = newValue;
105 // sort(0, _realLength - 1);
106 }
107 }
108
109 void sort(int start, int end) {
110 if (start >= end) return;
111 var pl = start, pr = end, key = _array[pl];
112 while (pl < pr) {
113 while (_array[pr] >= key && pr > pl) pr--;
114 if (pr > pl) {
115 _array[pl] = _array[pr];
116 pl++;
117 }
118 while (_array[pl] <= key && pl < pr) pl++;
119 if (pl < pr) {
120 _array[pr] = _array[pl];
121 pr--;
122 }
123 }
124 _array[pl] = key;
125
126 sort(start, pl - 1);
127 sort(pl + 1, end);
128 }
129
130 void display() {
131 var sb = StringBuffer();
132 sb.write('[');
133 if (_realLength > 0) {
134 for (var i = 0; i < _realLength - 1; i++) {
135 sb.write('${_array[i]}, ');
136 }
137 sb.write('${_array[_realLength - 1]}');
138 }
139 sb.write(']');
140 print(sb.toString());
141 }
142 }
143
144 void main() {
145 var arr = OrderedArray(100);
146 arr.fill(0.2);
147 arr.display();
148
149 var key = _rnd.nextInt(_seed);
150 if (arr.insert(key)) {
151 print('insert \'$key\' successed.');
152 arr.display();
153 } else {
154 print('insert \'$key\' failed.\n');
155 }
156
157 key = _rnd.nextInt(_seed);
158 var pos = arr.find(key);
159 if (pos >= 0) {
160 print('found the key: $key at $pos\n');
161 } else {
162 print('can not find the key: $key\n');
163 }
164
165 key = _rnd.nextInt(_seed);
166 pos = arr.length ~/ 2;
167 var oldValue = arr[pos];
168 if (arr.modify(pos, key)) {
169 print('modified the old value ($oldValue) to the new: $key at $pos');
170 }
171 pos = arr.length;
172 oldValue = arr[pos];
173 if (arr.modify(pos, key)) {
174 print('modified the old value ($oldValue) to the new: $key at $pos\n');
175 } else {
176 print('the position to be modified is out of bound.\n');
177 }
178 arr.display();
179
180 arr[0] = _rnd.nextInt(_seed);
181 arr[arr.length] = _rnd.nextInt(_seed);
182 arr.display();
183
184 print('now sort the array:');
185 arr.sort(0, arr.length - 1);
186 arr.display();
187
188 key = _rnd.nextInt(_seed);
189 if (arr.delete(key)) {
190 arr.display();
191 print('has deleted the key: $key');
192 } else {
193 print('can not find the key to delete: $key');
194 }
195
196 print('now delete the key: ${arr[arr.length ~/ 2]}');
197 arr.delete(arr[arr.length ~/ 2]);
198 arr.display();
199 }