数据结构与算法之数组（1）——in dart

 import 'dart:math' show Random;

 List<int> _array;
 final _rnd = Random();
 final _capacity = 100;
 final _max = 100;
 var _length = 0;

 void main() {
   _array = List<int>(_capacity);
   // _array = List<int>.filled(_capacity, -1);

   _insert();
   _display();

   var key = _rnd.nextInt(_max);
   print('the find key is: $key');
   var pos = _find(key);
   if (pos < 0) {
     print('can not find the key: $key.\n');
   } else {
     print('found the key at: $pos.\n');
   }

   var oldValue = _modify(_length ~/ 2, _rnd.nextInt(_max));
   if (oldValue != null) {
     print('has modified! and oldValue is $oldValue.\n');
   }
   _display();

   _delete(_rnd.nextInt(_max));
   _display();
 }

 void _insert() {
   for (var i = 0; i < _capacity ~/ 2; i++) {
     _array[i] = _rnd.nextInt(_max);
     _length++;
   }
 }

 void _display() {
   var sb = StringBuffer();
   for (var i = 0; i < _length; i++) {
     sb.write('${_array[i]}, ');
   }
   var s = sb.isEmpty ? '' : sb.toString().substring(0, sb.length - 2);
   print('$s\n');
 }

 int _find(int key) {
   var index = -1;
   for (var i = 0; i < _length; i++) {
     if (_array[i] == key) {
       index = i;
       break;
     }
   }
   return index;
 }

 int _modify(int pos, int newValue) {
   int oldValue;
   if (pos > _length - 1) {
     print('out of bound!\n');
   } else {
     print(
         'will modify the value(${_array[pos]}) of array[$pos] to new value: $newValue');
     oldValue = _array[pos];
     _array[pos] = newValue;
   }
   return oldValue;
 }

 void _delete(int key) {
   print('the deleted key is: $key');
   var pos = _find(key);
   if (pos < 0) {
     print('can not find the key: $key!\n');
   } else {
     print('the index of deleted key is: $pos\n');
     for (var i = pos; i < _length - 1; i++) {
       _array[i] = _array[i + 1];
     }
     _length--;
   }
 }

这是用dart语言实现的数组，因为dart内置List，且面向对象，本代码故意没有使用类和内置的List的部分特性。为了保证运行效果，采用随机数进行增删改查。