1887-ReductionOperationsToMakeTheArrayElementsEqual.go

package main

// 1887. Reduction Operations to Make the Array Elements Equal
// Given an integer array nums, your goal is to make all elements in nums equal. 
// To complete one operation, follow these steps:
//     1. Find the largest value in nums. Let its index be i (0-indexed) and its value be largest. 
//        If there are multiple elements with the largest value, pick the smallest i.
//     2. Find the next largest value in nums strictly smaller than largest. 
//        Let its value be nextLargest.
//     2. Reduce nums[i] to nextLargest.

// Return the number of operations to make all elements in nums equal.

// Example 1:
// Input: nums = [5,1,3]
// Output: 3
// Explanation: It takes 3 operations to make all elements in nums equal:
// 1. largest = 5 at index 0. nextLargest = 3. Reduce nums[0] to 3. nums = [3,1,3].
// 2. largest = 3 at index 0. nextLargest = 1. Reduce nums[0] to 1. nums = [1,1,3].
// 3. largest = 3 at index 2. nextLargest = 1. Reduce nums[2] to 1. nums = [1,1,1].

// Example 2:
// Input: nums = [1,1,1]
// Output: 0
// Explanation: All elements in nums are already equal.

// Example 3:
// Input: nums = [1,1,2,2,3]
// Output: 4
// Explanation: It takes 4 operations to make all elements in nums equal:
// 1. largest = 3 at index 4. nextLargest = 2. Reduce nums[4] to 2. nums = [1,1,2,2,2].
// 2. largest = 2 at index 2. nextLargest = 1. Reduce nums[2] to 1. nums = [1,1,1,2,2].
// 3. largest = 2 at index 3. nextLargest = 1. Reduce nums[3] to 1. nums = [1,1,1,1,2].
// 4. largest = 2 at index 4. nextLargest = 1. Reduce nums[4] to 1. nums = [1,1,1,1,1].

// Constraints:
//     1 <= nums.length <= 5 * 10^4
//     1 <= nums[i] <= 5 * 10^4

import "fmt"
import "sort"

func reductionOperations(nums []int) int {
    sort.Ints(nums)
    res, steps, first, prev := 0, 0, nums[0], nums[0]
    for _, v := range nums {
        if v == first { continue }
        if v != prev {
            steps++
        }
        if steps > 0 {
            res += steps
        }
        prev = v
    }
    return res
}

func reductionOperations1(nums []int) int {
    sort.Ints(nums)
    res, count := 0, 0
    for i := 0; i < len(nums) - 1; i++ {
        if nums[i] != nums[i + 1] {
            count++
        }
        res += count
    }
    return res
}

func main() {
    // Example 1:
    // Input: nums = [5,1,3]
    // Output: 3
    // Explanation: It takes 3 operations to make all elements in nums equal:
    // 1. largest = 5 at index 0. nextLargest = 3. Reduce nums[0] to 3. nums = [3,1,3].
    // 2. largest = 3 at index 0. nextLargest = 1. Reduce nums[0] to 1. nums = [1,1,3].
    // 3. largest = 3 at index 2. nextLargest = 1. Reduce nums[2] to 1. nums = [1,1,1].
    fmt.Println(reductionOperations([]int{5,1,3})) // 3
    // Example 2:
    // Input: nums = [1,1,1]
    // Output: 0
    // Explanation: All elements in nums are already equal.
    fmt.Println(reductionOperations([]int{1,1,1})) // 0
    // Example 3:
    // Input: nums = [1,1,2,2,3]
    // Output: 4
    // Explanation: It takes 4 operations to make all elements in nums equal:
    // 1. largest = 3 at index 4. nextLargest = 2. Reduce nums[4] to 2. nums = [1,1,2,2,2].
    // 2. largest = 2 at index 2. nextLargest = 1. Reduce nums[2] to 1. nums = [1,1,1,2,2].
    // 3. largest = 2 at index 3. nextLargest = 1. Reduce nums[3] to 1. nums = [1,1,1,1,2].
    // 4. largest = 2 at index 4. nextLargest = 1. Reduce nums[4] to 1. nums = [1,1,1,1,1].
    fmt.Println(reductionOperations([]int{1,1,2,2,3})) // 4

    fmt.Println(reductionOperations1([]int{5,1,3})) // 3
    fmt.Println(reductionOperations1([]int{1,1,1})) // 0
    fmt.Println(reductionOperations1([]int{1,1,2,2,3})) // 4
}