main.go

// Source: https://leetcode.com/problems/apply-operations-to-an-array
// Title: Apply Operations to an Array
// Difficulty: Easy
// Author: Mu Yang <http://muyang.pro>

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// You are given a **0-indexed** array `nums` of size `n` consisting of **non-negative** integers.
//
// You need to apply `n - 1` operations to this array where, in the `i^th` operation (**0-indexed**), you will apply the following on the `i^th` element of `nums`:
//
// - If `nums[i] == nums[i + 1]`, then multiply `nums[i]` by `2` and set `nums[i + 1]` to `0`. Otherwise, you skip this operation.
//
// After performing **all** the operations, **shift** all the `0`'s to the **end** of the array.
//
// - For example, the array `[1,0,2,0,0,1]` after shifting all its `0`'s to the end, is `[1,2,1,0,0,0]`.
//
// Return the resulting array.
//
// **Note** that the operations are applied **sequentially**, not all at once.
//
// **Example 1:**
//
// ```
// Input: nums = [1,2,2,1,1,0]
// Output: [1,4,2,0,0,0]
// Explanation: We do the following operations:
// - i = 0: nums[0] and nums[1] are not equal, so we skip this operation.
// - i = 1: nums[1] and nums[2] are equal, we multiply nums[1] by 2 and change nums[2] to 0. The array becomes [1,**4**,**0**,1,1,0].
// - i = 2: nums[2] and nums[3] are not equal, so we skip this operation.
// - i = 3: nums[3] and nums[4] are equal, we multiply nums[3] by 2 and change nums[4] to 0. The array becomes [1,4,0,**2**,**0**,0].
// - i = 4: nums[4] and nums[5] are equal, we multiply nums[4] by 2 and change nums[5] to 0. The array becomes [1,4,0,2,**0**,**0**].
// After that, we shift the 0's to the end, which gives the array [1,4,2,0,0,0].
// ```
//
// **Example 2:**
//
// ```
// Input: nums = [0,1]
// Output: [1,0]
// Explanation: No operation can be applied, we just shift the 0 to the end.
// ```
//
// **Constraints:**
//
// - `2 <= nums.length <= 2000`
// - `0 <= nums[i] <= 1000`
//
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package main

func applyOperations(nums []int) []int {
	n := len(nums)
	res := make([]int, n)
	resLen := 0

	for i := range n - 1 {
		if nums[i] == 0 {
			continue
		}
		if nums[i] == nums[i+1] {
			nums[i] *= 2
			nums[i+1] = 0
		}
		res[resLen] = nums[i]
		resLen++
	}
	res[resLen] = nums[n-1]

	return res
}