An array is an index-based data structure, which means every element is referred by an index. Array data are stored in sequential memory. The index runs from 0 to the array size minus one. The size of an array should be specified when initializing an array in Java. Here is implementation of array operations – add, remove, search and traversal.
Table of Content
Add element
Add element at the end, or at the given index. In Java, you need check whether you have reached the max size.
Java
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public class Array<T> { private T[] array; private int maxSize ; private int length = 0; //Constructor, Time O(1), Space O(1) @SuppressWarnings("unchecked") public Array(int size) { maxSize = size; array = (T[]) new Object[maxSize]; } //Add one element at the end, Time O(1), Space O(1) public void add(T value) { if( length == maxSize) { System.out.println("reach max size!"); return; } array[length] = value; length++; } //Add one element at index, Time O(n), Space O(1) public void insertAt(T value, int index) { if (length+1 > maxSize ) { System.out.println("reach max size!"); return; } if (index < 0 || index > length) { System.out.println("invalid index"); return; } length++; for (int i = length-1; i > index; i--) { array[i] = this.array[i-1]; } array[index] = value; } } |
Javascript
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class Array{ //Constructor, Time O(1), Space O(1) constructor() { this.length = 0; this.array = {}; } //Add one element, Time O(1), Space O(1) insert(value) { this.array[this.length] = value; this.length++; } //Add one element at index, Time O(n), Space O(1) insertAt(value, index) { if (index < 0 || index > this.length) { console.log("invalid index"); return; } this.length++; for (let i = this.length; i >= index; i--) { this.array[i] = this.array[i-1]; } this.array[index] = value; } } |
Python
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class Array: #Constructor, Time O(1), Space O(1) def __init__(self): self.length = 0 self.array = {} #Add one element, Time O(1), Space O(1) def add(self, value) : self.array[self.length] = value self.length += 1 #Add one element at index, Time O(n), Space O(1) def insertAt(self, value, index) : if index < 0 or index > self.length : print("invalid index") return self.length += 1 for i in range (self.length-1, index, -1) : self.array[i] = self.array[i-1] self.array[index] = value |
Doodle
Delete element
Delete the element by key or by index. You need to move the following elements to their preceding position.
Java
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//Delete by key, Time O(n), Space O(1), n is array length public void delete(T key) { if (search(key) <0) { System.out.println("key not found!"); return; } int i, j; for (i = 0; i < length; i++) { if (array[i] == key) break; } for (j = i; j < length-1; j++) array[j] = array[j+1]; length--; } //Delete element at index, Time O(n), Space O(1), n is array length public void deleteAt(int index) { if (index >= length || index < 0) { System.out.println("invalid index!"); return; } for(int i = index; i < length-1; i++) { array[i] = array[i+1]; } length--; } |
Javascript
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//Delete by key, Time O(n), Space O(1), n is array length delete (key) { if (this.search(key) == -1) { console.log("key not found!"); return; } var i, j; for (i = 0; i < this.length; i++) { if (this.array[i] == key) break; } for (j = i; j < this.length-1; j++) this.array[j] = this.array[j+1]; this.length--; } //Delete element at index, Time O(n), Space O(1), n is array length deleteAt(index) { if (index >= this.length || index < 0) { console.log("invalid index!"); return; } for (let i = index; i < this.length-1; i++) { this.array[i]=this.array[i+1]; } this.length--; } |
Python
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#Delete by key, Time O(n), Space O(1), n is array length def delete (self, key) : if self.search(key) == -1 : print("key not found!") return start = 0 for i in range ( 0, self.length, +1): if (self.array[i] == key): start = i; break for j in range(start, self.length-1, +1): self.array[j] = self.array[j+1] self.length -= 1 #Delete element at index, Time O(n), Space O(1), n is array length def deleteAt(self, index) : if index >= self.length or index < 0 : print("invalid index!") return for i in range (index, self.length-1, +1): self.array[i] = self.array[i+1] self.length -= 1 |
Doodle
Linear search
Starting from the index 0, compare each element in the array with the key . Return the first matched element’s index. If the key is not found, return -1.
Java
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//Search by key, Time O(n), Space O(1) public int search(T key) { int i; for (i = 0; i < length; i++) { if (array[i] == key) break; } if (i == length) return -1; else return i; } |
Javascript
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//Search by key, Time O(n), Space O(1) search(key) { for (var i = 0; i < this.length; i++) { if (this.array[i] == key) { return i; } } return -1; } |
Python
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#Search by key, Time O(n), Space O(1) def search(self, key) : for i in range(0, self.length, +1) : if self.array[i] == key: return i return -1 |
Doodle
Print elements
Print all elements in the array from index 0 to the last.
Java
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//Print array, Time O(n), Space O(1) public void print() { for (int i = 0; i < length; i++) System.out.print(array[i] + " "); System.out.println(); } |
Javascript
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//Print array, Time O(n), Space O(1) print() { var s = ''; for (var i = 0; i < this.length; i++) { s += this.array[i] + ' '; } console.log('array is ' + s); } |
Python
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#Print array, Time O(n), Space O(1) def print(self) : for i in range( 0, self.length, +1): print(self.array[i], end = ' ' ) print() |
Doodle
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Array animated
Data structures and Java collections