3362. Zero Array Transformation III.cpp

[rishanmenezes]

PR Title: 3362. Zero Array Transformation III.cpp

Intuition

The problem asks us to transform an array of non-negative integers into an array of all zeros using a specific operation. The operation involves choosing an index i and a non-negative integer x, then subtracting x from nums[i] and nums[i+1]. We want to find the minimum total sum of x values used.

Let's analyze the operation. When we subtract x from nums[i] and nums[i+1], it means nums[i] and nums[i+1] are reduced by the same amount. This suggests a greedy approach from left to right.

Consider nums[0]. To make nums[0] zero, we must apply an operation at index 0 with x = nums[0]. This will also affect nums[1]. After this operation, nums[0] becomes zero. We then move to nums[1] (which has been modified) and repeat the process.

Approach

Let's try a direct greedy approach. Iterate from i = 0 to n-1. For each nums[i], if nums[i] is not zero, we must perform an operation at index i to make it zero. The value of x for this operation must be nums[i] itself. This operation will also subtract nums[i] from nums[i+1] (if i+1 < n). We add nums[i] to our total operations count.

Example: nums = [1, 2, 3]

i = 0: nums[0] = 1. We need to subtract 1 from nums[0] and nums[1]. x = 1. Total operations = 1. nums becomes [0, 1, 3]

i = 1: nums[1] = 1. We need to subtract 1 from nums[1] and nums[2]. x = 1. Total operations = 1 + 1 = 2. nums becomes [0, 0, 2]

i = 2: nums[2] = 2. We need to subtract 2 from nums[2] (and nums[3] if it existed, but it doesn't). x = 2. Total operations = 2 + 2 = 4. nums becomes [0, 0, 0]

This greedy strategy seems to work. For each element nums[i], if it's positive, we must reduce it to zero. The only way to reduce nums[i] without affecting nums[0...i-1] (which we've already made zero) is to apply the operation at index i. The amount we subtract, x, must be exactly nums[i] to make it zero. This x then also reduces nums[i+1].

Code Solution (C++)

class Solution {public:    long long zeroArray    (vector<int>& nums) {        long long total_operations         = 0;        int n = nums.size();        for (int i = 0; i < n; ++i)         {            if (nums[i] > 0) {                total_operations +=                 nums[i];                if (i + 1 < n) {                    nums[i+1] -=                     nums[i];                    // Ensure nums[i                    +1] does not                     become negative                    if (nums[i+1] <                     0) {                        nums[i+1] =                         0;                    }                }                nums[i] = 0; // nums                [i] is now zero            }        }        return total_operations;    }};
Related Issues
By submitting this PR, I confirm that:

• This is my original work not totally AI generated
• [x]I have tested the solution thoroughly on leetcode
• I have maintained proper PR description format
• This is a meaningful contribution, not spam

Summary by Sourcery

New Features:

• Implement C++ solution for Zero Array Transformation III using a left-to-right greedy subtraction approach

[sourcery-ai]

Reviewer's Guide

Introduces a left-to-right greedy solution that zeros the array by subtracting each element’s value from itself and its neighbor, clamping negatives and summing the total operations.

Sequence diagram for the greedy zeroing process in zeroArray()

sequenceDiagram
participant Solution
participant nums
actor User
User->>Solution: Call zeroArray(nums)
Solution->>nums: Iterate from i = 0 to n-1
alt nums[i] > 0
    Solution->>nums: Subtract nums[i] from nums[i] and nums[i+1]
    Solution->>Solution: Add nums[i] to total_operations
    alt nums[i+1] < 0
        Solution->>nums: Set nums[i+1] = 0
    end
    Solution->>nums: Set nums[i] = 0
end
Solution-->>User: Return total_operations

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Class diagram for Solution and zeroArray() method

classDiagram
class Solution {
  +long long zeroArray(vector<int>& nums)
}
Solution : zeroArray(nums) -- Greedy left-to-right zeroing

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File-Level Changes

Change	Details	Files
Left-to-right greedy zeroing algorithm implemented	Initialize total_operations accumulator Iterate over each index and apply x=nums[i] when nums[i]>0 Subtract x from nums[i+1] and clamp it to zero if negative Accumulate x and set nums[i] to zero	3362. Zero Array Transformation III.cpp
Comprehensive in-code documentation and example added	Inserted problem statement and approach comments Provided a worked example with nums=[1,2,3] Annotated key steps and edge-case handling with inline comments	3362. Zero Array Transformation III.cpp

Possibly linked issues

• #3362: The PR provides the approach, intuition, and solution in code for Zero Array Transformation III, fulfilling the issue's requirements.

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[SjxSubham]

@rishanmenezes star the repo...

[rishanmenezes]

@rishanmenezes star the repo...

I have done it only merging the pr is remaining from your side