Given an array list **arr** and values **lowVal** and **highVal**. The task is to partition the array around the range such that the array List is divided into three parts.

1) All elements smaller than **lowVal** come first.

2) All elements in range **lowVal** to **highVVal** come next.

3) All elements greater than **highVVal** appear in the end.

The individual elements of three sets can appear in any order. You are required to return the modified arranged array.

**Note: **This is a switch-case version of Dutch National Flag algorithm which is used to in three way partition.

**Examples:**

Input: arr[] = {1, 14, 5, 20, 4, 2, 54, 20, 87, 98, 3, 1, 32} lowVal = 14, highVal = 20 Output: arr[] = {1, 5, 4, 2, 1, 3, 14, 20, 20, 98, 87, 32, 54} Input: arr[] = {1, 14, 5, 20, 4, 2, 54, 20, 87, 98, 3, 1, 32} lowVal = 20, highVal = 20 Output: arr[] = {1, 14, 5, 4, 2, 1, 3, 20, 20, 98, 87, 32, 54}

**Algorithm:**

- We create
**low = 0, mid = 0, high = arr.size();** - Now,
**arr**till mid is less than or equal to high i.e;**mid ≤ high**. - Now create another
**variable as value**, here we will be storing our condition which is used in switch case. - If
**arr.get(mid) < lowVal**then we will store**0**in the value. - If
**arr.get(mid) >= lowVal && arr.get(mid) ≤ highVal)**then store**1**in the value. - If
**arr.get(mid) > highVal**then we store**2**in the value. - Now check for the value in the switch.
- If it is
**0**then we swap elements from a position of**mid to low**and**low to mid**of the**arr**i.e; Collections.swap(arr, mid, low) then increment both mid and low i.e;**mid++; low++;**and finally break. - If it is
**1**then we**do not****swap**elements from their position because elements satisfying the second condition i.e., if the element is between lowVal and highVal it is kept as it is. We only swap elements satisfying only first and third conditions according to the statement. Then increment mid i.e; mid++; and finally, break. - If it is
**2**then we swap elements from a position of**mid to high**and**high to mid**of the arr i.e; Collections.swap(A, mid, high) then increment both mid and high i.e., mid++; high++; and finally break. - At last, return the ArrayList arr.

## Java

`// Dutch National Sort algorithm ` `// using switch in Java` ` ` `import` `java.io.*;` `import` `java.util.*;` ` ` `class` `GFG {` ` ` ` ` `static` `ArrayList<Integer>` ` ` `threeWayPartition(ArrayList<Integer> arr, ` `int` `lowVal,` ` ` `int` `highVal)` ` ` `{` ` ` `// dutch national sort algorithm` ` ` `// using switch` ` ` `int` `low = ` `0` `, mid = ` `0` `, high = arr.size() - ` `1` `;` ` ` ` ` `while` `(mid <= high) {` ` ` ` ` `int` `value;` ` ` ` ` `// satisfying consition 1` ` ` `if` `(arr.get(mid) < lowVal)` ` ` `value = ` `0` `;` ` ` ` ` `// satisfying condition 2` ` ` `else` `if` `(arr.get(mid) >= lowVal` ` ` `&& arr.get(mid) <= highVal)` ` ` `value = ` `1` `;` ` ` ` ` `// satisfying condition 3` ` ` `else` ` ` `value = ` `2` `;` ` ` ` ` `switch` `(value) {` ` ` ` ` `// incase of first condition, do this` ` ` `case` `0` `:` ` ` `Collections.swap(arr, mid, low);` ` ` `mid++;` ` ` `low++;` ` ` `break` `;` ` ` ` ` `// incase of second condition, do this` ` ` `case` `1` `:` ` ` `mid++;` ` ` `break` `;` ` ` ` ` `// incase of third condition, do this` ` ` `case` `2` `:` ` ` `Collections.swap(arr, mid, high);` ` ` `high--;` ` ` `break` `;` ` ` `}` ` ` `}` ` ` ` ` `// return the modified arraylist` ` ` `return` `arr;` ` ` `}` ` ` ` ` `public` `static` `void` `main(String[] args)` ` ` `{` ` ` ` ` `Scanner s = ` `new` `Scanner(System.in);` ` ` ` ` `// create an empty arraylist` ` ` `ArrayList<Integer> a = ` `new` `ArrayList<>();` ` ` ` ` `// add elements` ` ` `a.add(` `1` `);` ` ` `a.add(` `14` `);` ` ` `a.add(` `5` `);` ` ` `a.add(` `20` `);` ` ` `a.add(` `4` `);` ` ` `a.add(` `2` `);` ` ` `a.add(` `54` `);` ` ` `a.add(` `20` `);` ` ` `a.add(` `87` `);` ` ` `a.add(` `98` `);` ` ` `a.add(` `3` `);` ` ` `a.add(` `1` `);` ` ` `a.add(` `32` `);` ` ` ` ` `// stores the modified arraylist` ` ` `ArrayList<Integer> res` ` ` `= threeWayPartition(a, ` `14` `, ` `20` `);` ` ` ` ` `// Output the arraylist` ` ` `for` `(` `int` `i = ` `0` `; i < ` `13` `; i++)` ` ` `System.out.print(res.get(i) + ` `" "` `);` ` ` `}` `}` |

**Output**

1 5 4 2 1 3 14 20 20 98 87 32 54

**Time Complexity: O(n)****Auxiliary Space: O(1)**

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