Package g2801_2900.s2826_sorting_three_groups

Class Solution

java.lang.Object
g2801_2900.s2826_sorting_three_groups.Solution
public class Solution extends java.lang.Object
2826 - Sorting Three Groups.

Medium

You are given a 0-indexed integer array nums of length n.

The numbers from 0 to n - 1 are divided into three groups numbered from 1 to 3, where number i belongs to group nums[i]. Notice that some groups may be empty.

You are allowed to perform this operation any number of times:

  • Pick number x and change its group. More formally, change nums[x] to any number from 1 to 3.

A new array res is constructed using the following procedure:

  1. Sort the numbers in each group independently.
  2. Append the elements of groups 1, 2, and 3 to res in this order.

Array nums is called a beautiful array if the constructed array res is sorted in non-decreasing order.

Return the minimum number of operations to make nums a beautiful array.

Example 1:

Input: nums = [2,1,3,2,1]

Output: 3

Explanation: It’s optimal to perform three operations:

  1. change nums[0] to 1.
  2. change nums[2] to 1.
  3. change nums[3] to 1.

After performing the operations and sorting the numbers in each group, group 1 becomes equal to [0,1,2,3,4] and group 2 and group 3 become empty. Hence, res is equal to [0,1,2,3,4] which is sorted in non-decreasing order.

It can be proven that there is no valid sequence of less than three operations.

Example 2:

Input: nums = [1,3,2,1,3,3]

Output: 2

Explanation: It’s optimal to perform two operations:

  1. change nums[1] to 1.
  2. change nums[2] to 1.

After performing the operations and sorting the numbers in each group, group 1 becomes equal to [0,1,2,3], group 2 becomes empty, and group 3 becomes equal to [4,5]. Hence, res is equal to [0,1,2,3,4,5] which is sorted in non-decreasing order.

It can be proven that there is no valid sequence of less than two operations.

Example 3:

Input: nums = [2,2,2,2,3,3]

Output: 0

Explanation: It’s optimal to not perform operations.

After sorting the numbers in each group, group 1 becomes empty, group 2 becomes equal to [0,1,2,3] and group 3 becomes equal to [4,5]. Hence, res is equal to [0,1,2,3,4,5] which is sorted in non-decreasing order.

Constraints:

  • 1 <= nums.length <= 100
  • 1 <= nums[i] <= 3

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    minimumOperations(java.util.List<java.lang.Integer> nums)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • minimumOperations

      public int minimumOperations(java.util.List<java.lang.Integer> nums)