High Array

Rewritten Low Array using more OOP way. Describes LinerSearch in Arrays.

The Low Array program is essentially consists of one big method. We can reap many benefits by dividing the program into classes. The data storage structure itself is one candidate, and the part of the program that uses this data structure is another. By dividing the program into these two classes, we can clarify the functionality of the program, making it easier to design and understand (and in real programs to modify and maintain).

In Low Array we used an array as a data storage structure, but we treated it simply as a language element. Now we’ll encapsulate the array in a class, called LowArray. Our first design of the LowArray class won’t be entirely successful, but it will demonstrate the need for a better approach.

$ dart 01_array/high_array.dart

import 'dart:io';

class HighArray {
  List<int> a; // ref to array a
  int nElems; // number of data items

  // Constructor
  HighArray(int max) {
    a = new List<int>(max); // create array (List in Dart)
    nElems = 0; // initialize items count
  }

  /// Find specified value
  bool find(int searchKey) {
    int j;
    // for each element
    for(j = 0; j < nElems; j++) {
      // found item?
      if (a[j] == searchKey) {
        break; // exit loop before end
      }
    }
    // is end of array
    if (j == nElems) {
      return false;
    } else {
      return true;
    }
  }

  /// Insert element into array
  void insert(int value) {
    a[nElems] = value; // insert it
    nElems ++; // increment size
  }

  /// Delete element from array
  bool delete(int value) {
    int j;
    for(j = 0; j < nElems; j++) {
      if (value == a[j]) {
        break;
      }
    }

    if(j == nElems) {
      return false;
    } else {
      for (int k = j; k < nElems - 1; k++) {
        a[k] = a[k + 1];
      }
      nElems --;
      return true;
    }
  }

  /// Display Array contents
  void display() {
    // for each element
    for(int j = 0; j < nElems; j++) {
      stdout.write('${a[j]} '); // display it
    }
    stdout.writeln(''); // add new line on the end
  }
}


void main() {
  int maxSize = 10; // array size
  HighArray array = new HighArray(maxSize); // create instance of HighArray

  // Insert 10 items
  array.insert(77);
  array.insert(99);
  array.insert(44);
  array.insert(55);
  array.insert(22);
  array.insert(88);
  array.insert(11);
  array.insert(0);
  array.insert(66);
  array.insert(33);

  // Display items
  array.display();

  // Search Element
  int searchKey = 35;
  if(array.find(searchKey)) {
    stdout.writeln('Found $searchKey');
  } else {
    stdout.writeln("Can't find $searchKey");
  }

  // Delete 3 items
  array.delete(0);
  array.delete(55);
  array.delete(99);

  // Display items again
  array.display();
}