步步为营，蚕食数据结构与算法---（一）数组篇（上篇）

　　数组是最基础的数据结构之一，也是很多高级数据结构的基础。

　　我们简单复习一下数组的创建与遍历，先做一下热身，后面逐渐一步步实现自己的数组

　　我们的开发环境主要是JDK1.8,c++11编辑工具是 jetbrains的强大开发工具 IteliJ（java），Clion（c++）

　　Java版：

 1 public class Main {
 2     public static void main(String[] args){
 3         int [] arr = new int[10];//init a new array with asigned prams
 4         for(int i = 0 ;i < arr.length ; i++){
 5 
 6             arr[i] = i ;
 7            System.out.println(arr[i]);}
 8         System.out.println("*****************************");
 9         int scores[] = new int[]{23,44,54};//please be noted diffrent ways of creating a new array and diffrent ways to iterate array
10 
11         for( int i = 0 ; i < scores.length ; i ++)
12             System.out.println(scores[i]);
13         System.out.println("*****************************");
14         for(int score : scores)
15             System.out.println(score);
16         System.out.println("*****************************");
17         scores[0] = 88 ;
18         for( int i = 0 ; i< scores.length ; i ++)
19             System.out.println(scores[i]);
20 
21     }
View Code

　　C++版：

#include <iostream>

int main() {
    int arr[10];
    for(int i = 0 ; i < 10 ; i++){
        arr[i] = i;
        std::cout << arr[i] <<" ";
    }
    std::cout << std::endl;
    int scores[] = {23,34,45};
    for(int i = 0; i < sizeof(scores)/ sizeof(int) ; i++){
        std::cout << scores[i] <<" ";
    }
    std::cout<<std::endl;
    scores[0] = 88;
    for(int i = 0 ;i  < sizeof(scores)/ sizeof(int); i++){
        std::cout << scores[i] << " ";
    }
    std::cout << std::endl;
    return 0;
}
View Code

　　首先我们创造自己的数组，在Java中，要创建自己的Array类，

Java版：

 1 public class Array {
 2     private int[] data;
 3     private int size;
 4     //constructor ,create Array with the input param "capacity"
 5     public Array(int capacity){
 6         data = new int[capacity];
 7         size = 0;
 8     }
 9     //constructor without params,our default capacity is 10
10     public Array(){
11         this(10);
12     }
13     //get the capacity of this array
14     public int getCapacity(){
15         return data.length;
16     }
17     //get the amount of elements of this array
18     public int getSize(){
19         return size;
20     }
21     //judge whether this array is empty or not
22     public boolean isEmpty(){
23         return size==0;
24     }
25 }
View Code

C++版：

 1 class Array {
 2 private:
 3     int *data;
 4     int size;
 5     int capacity;
 6 
 7 public:
 8     Array(int capacity){
 9         data = new int[capacity];
10         size = 0 ;
11         this->capacity = capacity;
12     }
13     Array(){
14         data = new int[10];
15         size = 0 ;
16         capacity = 10;
17 
18     }
19     int getCapcity(){
20         return capacity;
21     }
22     int getSize(){
23         return size;
24 
25     }
26     bool isEmpty(){
27         return size == 0;
28     }
29 
30 };
View Code

上面的Array类并不完善，我们将对其进行改进和提升

以Java为例：我们向Array中所有元素 后面添加一个元素，则有代码：

 1 public void addLast(int e){
 2         //judge whether can we add a new element
 3         if(size == data.length){
 4             throw new IllegalArgumentException("AddLust failed,the array is full");
 5         }
 6         //asign  the new last element
 7         data[size] = e ;
 8         //maintain the size of the array
 9         size ++ ;
10     }
View Code

继续我们创建为索引位置的插入一个元素的方法：

 1 public void add(int index ,int e){
 2         if(size ==data.length)
 3             throw new IllegalArgumentException("AddLust failed,the array is full");
 4 
 5         if(index < 0 || index > size) {
 6             throw new IllegalArgumentException("Add failed. the range of index must within [0,size)");
 7         }
 8          for(int i = size - 1 ;i >= index ; i--){//move elements from the tail of the array
 9             data[i+1] = data[i];
10          }
11         data[index] = e ;
12         size++;
13 
14     }
View Code

 

 

在插入元素时的逻辑如下：插入位置前面的元素不变，插入位置及其插入位置以后的元素均后移一位，空出的位置（也就是插入位置）插入新元素，在插入时我们采用从数组尾端开始移动，这是这段代码的巧妙所在

这时我们观察新加入的两个方法，似乎有重复，可以因为第二个方法明显包含了第一种方法，因此我们可以对代码进行优化，直接将第一种方法优化：

public void addLast(int e){

        add(size,e);
    }

同理我们也可以添加新的方法，在所有元素前面添加一个新元素：

public void addFirst(int e){
        add(0,e);
    }

获取索引位置的元素：

 

 //get elements by given index
    public int get(int index){
        if(index < 0 ||index >= size)
            throw new IllegalArgumentException("Get failed,the index must be a non negative number that smaller than the size");
        return data[index];
    }

根据索引替换元素：

//change the elements by elements
    public void set(int index,int e){
        if(index < 0 ||index >= size)
            throw new IllegalArgumentException("Get failed,the index must be a non negative number that smaller than the size");
        data[index] = e ;
    }

方便了解数组元素：

@Override
    public String toString(){
        StringBuilder res = new StringBuilder();
        res.append(String.format("Array: size = %d,capacity = %d\n", size, data.length));
        res.append('[');
        for(int i = 0 ; i < size ; i++){
            res.append(data[i]);
            if(i != size - 1)
                res.append(", ");
        }
        res.append(']');
        return res.toString();
    }

测试Array类：

public class Main {
    public static void main(String[] args){
        Array arr = new Array(20);
        for(int i = 0 ; i < 10 ; i++){
            arr.addLast(i);
        }
        System.out.println(arr);
        arr.add(1,12);
        System.out.println(arr);

        arr.addFirst(-1);
        System.out.println(arr);
    }
}

测试结果：

Array: size = 10,capacity = 20
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
Array: size = 11,capacity = 20
[0, 12, 1, 2, 3, 4, 5, 6, 7, 8, 9]
Array: size = 12,capacity = 20
[-1, 0, 12, 1, 2, 3, 4, 5, 6, 7, 8, 9]

综合到目前我们的Array类的代码：

Java版：

 1 public class Array {
 2     private int[] data;
 3     private int size;
 4     //constructor ,create Array with the input param "capacity"
 5     public Array(int capacity){
 6         data = new int[capacity];
 7         size = 0;
 8     }
 9     //constructor without params,our default capacity is 10
10     public Array(){
11         this(10);
12     }
13     //get the capacity of this array
14     public int getCapacity(){
15         return data.length;
16     }
17     //get the amount of elements of this array
18     public int getSize(){
19         return size;
20     }
21     //judge whether this array is empty or not
22     public boolean isEmpty(){
23         return size==0;
24     }
25     //enrich our Array----part 2
26     public void addLast(int e){
27 //        //judge whether can we add a new element
28 //        if(size == data.length){
29 //            throw new IllegalArgumentException("AddLust failed,the array is full");
30 //        }
31 //        //asign  the new last element
32 //        data[size] = e ;
33 //        //maintain the size of the array
34 //        size ++ ;
35         add(size,e);
36     }
37     public void addFirst(int e){
38         add(0,e);
39     }
40     public void add(int index ,int e){
41         if(size ==data.length)
42             throw new IllegalArgumentException("AddLust failed,the array is full");
43 
44         if(index < 0 || index > size) {
45             throw new IllegalArgumentException("Add failed. the range of index must within [0,size)");
46         }
47          for(int i = size - 1 ;i >= index ; i--){//move elements from the tail of the array
48             data[i+1] = data[i];
49          }
50         data[index] = e ;
51         size++;
52 
53     }
54     //get elements by given index
55     public int get(int index){
56         if(index < 0 ||index >= size)
57             throw new IllegalArgumentException("Get failed,the index must be a non negative number that smaller than the size");
58         return data[index];
59     }
60 
61     //change the elements by elements
62     public void set(int index,int e){
63         if(index < 0 ||index >= size)
64             throw new IllegalArgumentException("Get failed,the index must be a non negative number that smaller than the size");
65         data[index] = e ;
66     }
67     @Override
68     public String toString(){
69         StringBuilder res = new StringBuilder();
70         res.append(String.format("Array: size = %d,capacity = %d\n", size, data.length));
71         res.append('[');
72         for(int i = 0 ; i < size ; i++){
73             res.append(data[i]);
74             if(i != size - 1)
75                 res.append(", ");
76         }
77         res.append(']');
78         return res.toString();
79     }
80 
81 
82 }
View Code

C++版Array类：

 1 #include <iostream>
 2 #include <cassert>
 3 
 4 class Array {
 5 private:
 6     int *data;
 7     int size;
 8     int capacity;
 9 
10 public:
11     Array(int capacity) {
12         data = new int[capacity];
13         size = 0;
14         this->capacity = capacity;
15     }
16 
17     Array() {
18         data = new int[10];
19         size = 0;
20         capacity = 10;
21     }
22 
23     int getCapacity() {
24         return capacity;
25     }
26 
27     int getSize() {
28         return size;
29     }
30 
31     bool isEmpty() {
32         return size == 0;
33     }
34 
35     void add(int index, int e) {
36         assert(size < capacity && index >= 0 && index <= size);
37         for (int i = size - 1; i >= index; --i) {
38             data[i + 1] = data[i];
39         }
40         data[index] = e;
41         size++;
42     }
43 
44     void addFirst(int e) {
45         add(0, e);
46     }
47 
48     void addLast(int e) {
49         add(size, e);
50     }
51 
52     int get(int index) {
53         assert(index >= 0 && index < size);
54         return data[index];
55     }
56 
57     void set(int index, int e) {
58         assert(index >= 0 && index < size);
59         data[index] = e;
60     }
61 
62   
63     void print() {
64         std::cout << "Array: size = " << size << ", capacity = " << getCapacity() << std::endl;
65         toPrint();
66     std::cout << std::endl;
67     }
68 
69     void toPrint() {
70         std::cout << "[";
71         for (int i = 0; i < size; ++i) {
72             std::cout << data[i];
73             if (i != size - 1) {
74                 std::cout << ", ";
75             }
76         }
77         std::cout << "]";
78     }
79 };
View Code

C++测试：

 1 #include <iostream>
 2 #include "Array.h"
 3 
 4 int main() {
 5     Array *array = new Array(20);
 6     for (int i = 0; i < 10; ++i) {
 7         array->addLast(i);
 8     }
 9     array->print();
10     array->add(1, 100);
11     array->addFirst(-1);
12     array->print();
13     return 0;
14 }

测试结果：

1 C:\Users\SAMSUNG\CLionProjects\DataStructrus\cmake-build-debug\DataStructrus.exe
2 Array: size = 10, capacity = 20
3 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
4 Array: size = 12, capacity = 20
5 [-1, 0, 100, 1, 2, 3, 4, 5, 6, 7, 8, 9]
6 
7 Process finished with exit code 0

 

posted @ 2018-12-19 19:36  cuckoonuts  阅读(188)  评论(0)    收藏  举报