Day 20 - Array Partition

Write a program to divide the given array into sub arrays where each sub array is of the length equal to the given partition size.

Example

input: partition([1,2,3,4,5,6,7,8], 2)
output: [[1, 2], [3, 4], [5, 6], [7, 8]]
   
input: partition([1,2,3,4,5,6,7], 2)
output: [[1, 2], [3, 4], [5, 6], [7]]

JavaScript Solution(s)

Solution 1

A very simple solution, all we have to is loop through i=0 to array length. In each iteration we check whether current iteration (i) is divisible by size or not, if it is not divisible, we add the current element in toBeAdded array otherwise we push the toBeAdded array into partitionedArray. Also, we check that toBeAdded is not wmpty otherwise it will push an empty array to partitionedArray

function partition (array, size) {
    let partitionedArray = [],
        toBeAdded = [];

    for (let i=0; i<array.length; i++) {
        if ((i)%size === 0) {
            if (toBeAdded.length > 0)  partitionedArray.push (toBeAdded);
            toBeAdded = [];
        }
        toBeAdded.push (array[i]);
    }
    if (toBeAdded.length > 0)  partitionedArray.push (toBeAdded);
    return partitionedArray;
}

Solution 2

The second solution is also similar to the first one. Here, we create an empty array to hold partitions (let’s call the array partitionedArray). Now for each element in the “original” array, we retrieve the last element in partitionedArray . If the last element does not exist (in case of empty array), or if it’s size is equal to the partition size, we push a new partition array into the partitionedArray with the current element. Otherwise, we add the current element into the partition.

function partition (array, size) {
    let partitionedArray = [];

    for (let element of array) {
        let partition = partitionedArray[partitionedArray.length - 1];
        if (!partition || partition.length === size) {
            partitionedArray.push ([element]);
        } else {
            lastEle.push (element);
        }
    }

    return partitionedArray;
}

Solution 3

This method will use JavaScript’s slice method. This is probably the easiest method due to the inbuilt function slice.

How slice works

array.sllice (startIndex, endIndex); will return a subarray of array including elements from startIndex to endIndex (not including endIndex).

Steps

• Create an empty partitionedArray array
• run a while loop from index i=0 to less than “original” array.length
• Push a slice of length size from array to partitionedArray.
• index = index+size

function partition (array, size) {
    let partitionedArray = [], i=0;
    while (i<array.length) {
        partitionedArray.push (array.slice(i, i+size));
        i += size;
    }
    return partitionedArray;
}

Ruby Solution(s)

Solution

=begin
@author: aaditkamat
@date: 16/01/2019
=end
def partition(arr, n)
    result = []
    ctr = 0
    until ctr == arr.size do
      temp = []
        n.times do |i|
            temp += [arr[ctr]]
            ctr += 1
            if ctr == arr.size
                break
            end
      end
        result += [temp]
  end
    puts "The partitioned array is: #{result}"
end

def main
  print "Enter an array: "
    arr = gets.chomp!.gsub(/\[|\]/, '').split(',').map!{|x| x.to_i}
    print "Enter number of partitions: "
    n = gets.chomp!.to_i
    partition(arr, n)
end

main
=======
## Java Implementation

### [Solution](/day20/Java/Partitions.java)

```java
/**
 * @date 16/01/19
 * @author SPREEHA DUTTA
 */
import java.util.*;
public class Partitions {
    public static void main(String []args)
    {
        Scanner sc=new Scanner(System.in);
        int n,p,i,j;int k=0;
        System.out.println("Enter size of original array");
        n=sc.nextInt();
        int arr[]=new int[n];
        for(i=0;i<n;i++)
            arr[i]=sc.nextInt();
        System.out.println("Enter size of partition");
        p=sc.nextInt();
        for(i=0;i<arr.length;i=i+p)
        {
            int part[]=Arrays.copyOfRange(arr,i,i+p);
            k++;
            if(arr.length%2!=0 && k==(arr.length/p+1))
                p=arr.length%p;
            System.out.print("{ ");
            for(j=0;j<p;j++)
                System.out.print(part[j]+" ");
            System.out.print("}\n");
        }
    }
}

C++ Solution

Solution @divyakhetan

/**
 * @author divyakhetan
 * @date 16/1/2019
 */

#include<bits/stdc++.h>
using namespace std;

int main(){
	cout << "Enter length of 1st and 2nd array";
	int n1, n2;	
	cin >> n1 >> n2;
	int a[n1];
	int b[n2];
	for(int i = 0; i < n1; i++){
		cin >> a[i];
		
	}
	
	for(int i = 0; i < n2; i++){
		cin >> b[i];
	}
	
	for(int i = 0; i < n1; i++){
		for(int j = 0; j < n2; j++){
			cout << "[ " << a[i]  << " " << b[j] << " ] " << endl;
		}
	}
	return 0;
}