135. candy.cpp by kaif969 · Pull Request #258 · SjxSubham/Leetcode

kaif969 · 2025-10-29T12:12:25Z

PR Title Format: 135. candy.cpp

Intuition

We are given ratings of children standing in a line, and we must distribute candies such that:

Each child gets at least one candy.
Children with a higher rating than their immediate neighbors receive more candies.

The key idea is to traverse the ratings twice:

Once from left to right to handle increasing sequences.
Once from right to left to handle decreasing sequences.

This ensures both sides of each child are considered.

Approach

Initialize a count array of size n (number of children), with all values set to 1. This satisfies the minimum candy condition.
Left to Right Traversal:

Iterate from i = 1 to n - 1.
If ratings[i] > ratings[i - 1], set count[i] = count[i - 1] + 1.

Right to Left Traversal:

Iterate from i = n - 2 down to 0.
If ratings[i] > ratings[i + 1], set count[i] = max(count[i], count[i + 1] + 1) to satisfy both directions.

Sum all elements in the count array to get the minimum total candies.

Code Solution (C++)

   class Solution {
public:
    int candy(vector<int>& ratings) {
        int n = ratings.size();
        vector<int> count(n, 1);  // Step 1: Initialize with 1

        // Step 2: Left to Right
        for (int i = 1; i < n; i++) {
            if (ratings[i] > ratings[i - 1]) {
                count[i] = count[i - 1] + 1;
            }
        }

        // Step 3: Right to Left
        for (int i = n - 2; i >= 0; i--) {
            if (ratings[i] > ratings[i + 1]) {
                count[i] = max(count[i], count[i + 1] + 1);
            }
        }

        // Step 4: Total candies
        return accumulate(count.begin(), count.end(), 0);
    }
};

Related Issues

#229

By submitting this PR, I confirm that:

[✅] This is my original work not totally AI generated
[✅] 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 candy distribution algorithm in Solution class

Summary by Sourcery

New Features:

Add candy method in Solution class that uses a two-pass algorithm to distribute candies based on ratings

sourcery-ai · 2025-10-29T12:12:31Z

Reviewer's Guide

Introduces a greedy two-pass algorithm to distribute candies: initialize a count array with 1s, perform a left-to-right pass to handle ascending ratings, a right-to-left pass to adjust for descending ratings, then sum the results.

Class diagram for the new Solution class implementing candy distribution

classDiagram
class Solution {
  +int candy(vector<int>& ratings)
}

Flow diagram for the candy distribution algorithm

flowchart TD
    A["Start: ratings array"] --> B["Initialize count array with 1s"]
    B --> C["Left to Right: for i = 1 to n-1"]
    C --> D["If ratings[i] > ratings[i-1], count[i] = count[i-1] + 1"]
    D --> E["Right to Left: for i = n-2 down to 0"]
    E --> F["If ratings[i] > ratings[i+1], count[i] = max(count[i], count[i+1] + 1)"]
    F --> G["Sum count array for total candies"]
    G --> H["Return total candies"]

File-Level Changes

Change	Details	Files
Implemented greedy two-pass traversal	Initialize count vector with 1 for each child Left-to-right pass to increment counts on increasing ratings Right-to-left pass using max logic to adjust counts for decreasing ratings Sum up all counts with std::accumulate	`135. Candy.cpp`

Possibly linked issues

20. Valid Parentheses.cpp #135: The PR provides the exact C++ solution for LeetCode problem 135 Candy, implementing the two-pass algorithm detailed in the issue.

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github-actions

Thanks for raising the PR, the owner will be review it soon' keep patience, keep contributing>>>!!! make sure you have star ⭐ the repo

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SjxSubham · 2025-10-29T18:44:55Z

@kaif969 Star the repo as well...

…candy_problem

kaif969 · 2025-10-29T19:53:01Z

@SjxSubham

star the repo done.

Please merge my PR.

github-actions · 2025-10-29T19:59:32Z

🎉 Congrats on getting your PR merged in, @kaif969! 🙌🏼

Thanks for your contribution every effort helps improve the project.

Looking forward to seeing more from you! 🥳✨

Implement candy distribution algorithm in Solution class

9ce0d5f

github-actions bot reviewed Oct 29, 2025

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sourcery-ai bot reviewed Oct 29, 2025

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SjxSubham linked an issue Oct 29, 2025 that may be closed by this pull request

135: Candy #229

Closed

4 tasks

SjxSubham approved these changes Oct 29, 2025

View reviewed changes

Merge branch 'main' into feat/candy_problem

638ffd0

SjxSubham assigned kaif969 Oct 29, 2025

SjxSubham added the hacktoberest-accepted hacktoberfest-accepted label Oct 29, 2025

Merge branch 'main' of https://github.com/kaif969/Leetcode into feat/…

0478eea

…candy_problem

SjxSubham merged commit d79de5a into SjxSubham:main Oct 29, 2025
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Comments

135. candy.cpp#258

135. candy.cpp#258
SjxSubham merged 3 commits intoSjxSubham:mainfrom
kaif969:feat/candy_problem

kaif969 commented Oct 29, 2025 •

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Intuition

Approach

Code Solution (C++)

Related Issues

Summary by Sourcery

Summary by Sourcery

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Reviewer's Guide

Class diagram for the new Solution class implementing candy distribution

Flow diagram for the candy distribution algorithm

File-Level Changes

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🎉 Congrats on getting your PR merged in, @kaif969! 🙌🏼

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kaif969 commented Oct 29, 2025 •

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