2164. Sort Even and Odd Indices Independently #

Problem #

You are given a 0-indexed integer array nums. Rearrange the values of nums according to the following rules:

Sort the values at odd indices of nums in non-increasing order.
- For example, if nums = [4,**1**,2,**3**] before this step, it becomes [4,**3**,2,**1**] after. The values at odd indices 1 and 3 are sorted in non-increasing order.
Sort the values at even indices of nums in non-decreasing order.
- For example, if nums = [**4**,1,**2**,3] before this step, it becomes [**2**,1,**4**,3] after. The values at even indices 0 and 2 are sorted in non-decreasing order.

Return the array formed after rearranging the values of nums.

Example 1:

Input: nums = [4,1,2,3]
Output: [2,3,4,1]
Explanation:
First, we sort the values present at odd indices (1 and 3) in non-increasing order.
So, nums changes from [4,1,2,3] to [4,3,2,1].
Next, we sort the values present at even indices (0 and 2) in non-decreasing order.
So, nums changes from [4,1,2,3] to [2,3,4,1].
Thus, the array formed after rearranging the values is [2,3,4,1].

Example 2:

Input: nums = [2,1]
Output: [2,1]
Explanation:
Since there is exactly one odd index and one even index, no rearrangement of values takes place.
The resultant array formed is [2,1], which is the same as the initial array.

Constraints:

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

Problem Summary #

Given a 0-indexed integer array nums. Rearrange the values in nums according to the following rules:

Sort all values at odd indices of nums in non-increasing order. For example, if nums = [4,1,2,3] before sorting, after sorting the values at odd indices it becomes [4,3,2,1]. The values at odd indices 1 and 3 are rearranged in non-increasing order.
Sort all values at even indices of nums in non-decreasing order. For example, if nums = [4,1,2,3] before sorting, after sorting the values at even indices it becomes [2,1,4,3]. The values at even indices 0 and 2 are rearranged in non-decreasing order.

Return the array formed after rearranging the values of nums.

Solution Approach #

Simple problem. Sort the numbers at odd and even positions separately: numbers at odd positions from large to small, and numbers at even positions from small to large. Finally, combine them into one array.

Code #

package leetcode

import (
	"sort"
)

func sortEvenOdd(nums []int) []int {
	odd, even, res := []int{}, []int{}, []int{}
	for index, v := range nums {
		if index%2 == 0 {
			even = append(even, v)
		} else {
			odd = append(odd, v)
		}
	}
	sort.Ints(even)
	sort.Sort(sort.Reverse(sort.IntSlice(odd)))

	indexO, indexE := 0, 0
	for i := 0; i < len(nums); i++ {
		if i%2 == 0 {
			res = append(res, even[indexE])
			indexE++
		} else {
			res = append(res, odd[indexO])
			indexO++
		}
	}
	return res
}