Divide Chocolate

Updated on 29 May, 2025
Divide Chocolate header image

Problem Statement

In this scenario, you possess a chocolate bar that is segmented into multiple chunks, each characterized by an individual sweetness value provided by an array named sweetness. Your objective is to share this chocolate with k friends. The task involves making k cuts on the chocolate, thereby splitting it into k + 1 segments, ensuring each segment comprises consecutive chunks from the original array.

Your role as the sharer dictates that you will end up consuming the segment that has the lowest total sweetness out of the k + 1 segments, keeping generosity in mind. The problem asks to determine the strategy for cutting the bar in such a way that the segment you consume has the maximum sweetness possible, relative to all potential ways of segmenting the bar.

This involves finding an optimal cutting strategy that maximizes the minimum sweetness segment that you will eat.

Examples

Example 1

Input:

sweetness = [1,2,3,4,5,6,7,8,9], k = 5

Output:

6

Explanation:

You can divide the chocolate to [1,2,3], [4,5], [6], [7], [8], [9]

Example 2

Input:

sweetness = [5,6,7,8,9,1,2,3,4], k = 8

Output:

1

Explanation:

There is only one way to cut the bar into 9 pieces.

Example 3

Input:

sweetness = [1,2,2,1,2,2,1,2,2], k = 2

Output:

5

Explanation:

You can divide the chocolate to [1,2,2], [1,2,2], [1,2,2]

Constraints

  • 0 <= k < sweetness.length <= 104
  • 1 <= sweetness[i] <= 105

Approach and Intuition

The problem can be considered as a form of the "Partition to K Equal Sum Subsets" optimization problem, where the goal is to partition an array in a way that the smallest sum of the partitions is as large as possible. The solution entails a mix of binary search and greedy approaches to effectively find an optimal cut:

  1. Greedy Partitioning: Implementing a greedy algorithm helps determine whether it is possible to partition the chocolate bar such that each segment has at least x sweetness. This involves iterating over the sweetness array and partitioning it into segments where each segment at least has x total sweetness until we either successfully create k+1 segments or fail.

  2. Binary Search: The key insight for maximizing the minimum sweetness of the consumed segment is utilizing binary search across possible sweetness values (ranging from the minimal sweetness chunk to possibly the sum of all chunks divided by k+1).

    • Initialize the boundaries: Start with low as the smallest sweetness value in the array and high as the sum of all sweetness values divided by k+1. This high boundary ensures that even in the most skewed partition, each part can at least potentially hold this value.
    • Iterate and adjust boundaries: For each midpoint value in the current low to high range, use the greedy algorithm to check if it's possible to partition the bar such that each piece has at least the midpoint sweetness. Adjust the search space based on whether the partitioning is possible:
      • If partitioning is feasible, it implies that a larger minimum segment sweetness might be achievable, so adjust the lower boundary up.
      • If it's not feasible, reduce the upper boundary.

This approach is guided by the constraints and examples given, ensuring computational efficiency given the upper limits of sweetness.length and individual sweetness[i] values. The binary search narrows down the potential values for maximum minimal sweetness efficiently, while the greedy check offers a systematic way to validate each potential cut strategy.

Solutions

  • C++
  • Java
  • JavaScript
  • Python
cpp
class Solution {
public:
    int maximizeSweetness(vector<int>& sweets, int people) {
        int indiv = people + 1;
        int low = *min_element(sweets.begin(), sweets.end());
        int high = accumulate(sweets.begin(), sweets.end(), 0) / indiv;

        while (low < high) {
            int median = (low + high + 1) / 2;
            int currentSweet = 0;
            int count = 0;

            for (int sweet : sweets) {
                currentSweet += sweet;
                if (currentSweet >= median) {
                    count += 1;
                    currentSweet = 0;
                }
            }

            if (count >= indiv) {
                low = median;
            } else {
                high = median - 1;
            }
        }

        return high;
    }
};

This solution addresses the problem of dividing chocolate into the maximum possible minimum sweetness that each person can receive. The provided code is written in C++ and focuses on a binary search method to optimize the problem of distributing sweetness evenly among a specified number of people.

Explanation of the Code:

  • The function maximizeSweetness accepts a vector sweets, which contains the sweetness levels of various chocolate pieces, and an integer people, representing the number of people sharing these sweets.

  • The goal is to make divisions such that at least people + 1 individuals get at least a certain level of sweetness that is maximized.

  • int indiv = people + 1; declares the total individual divisions needed which is one more than the number of people.

  • The chocolate pieces' minimum sweetness is stored in low, while high is initialized to the average total sweetness per individual achieved by summing the entire sweetness and dividing it by indiv.

  • The main logic involves a binary search within the while loop where low is less than high. The median point of current low and high values determines the trial division of sweetness.

  • If the sum of chocolates currentSweet reaches or exceeds this median sweetness during distribution (for loop iterating over sweets), the count of such successful divisions increments. This distribution resets currentSweet to zero every time the division condition is satisfied.

  • Based on the successful divisions (count), if they meet or exceed the required individuals (indiv), the search boundary adjusts to potentially increase the minimum sweetness. Otherwise, it decreases to find the closest possible fit under the median condition.

  • The process iterates until the optimal division point of sweetness (high) is found.

In summary, the algorithm efficiently ensures that the distribution allows for the most equitable distribution of sweetness to just over the number of people required, using a binary search mechanism to find the maximum of the minimum possible distribution of sweetness per person.

java
class Solution {
    public int maxSweetnessDistribution(int[] sweetnessLevels, int k) {
        int peopleCount = k + 1;
        int low = Arrays.stream(sweetnessLevels).min().getAsInt();
        int high = Arrays.stream(sweetnessLevels).sum() / peopleCount;

        while (low < high) {
            int middle = (low + high + 1) / 2;
            int currentSweetness = 0;
            int peopleAssigned = 0;
            
            for (int current : sweetnessLevels) {
                currentSweetness += current;
                
                if (currentSweetness >= middle) {
                    peopleAssigned += 1;
                    currentSweetness = 0;
                }
            }
            
            if (peopleAssigned >= peopleCount) {
                low = middle;
            } else {
                high = middle - 1;
            }
        }
        
        return high;
    }
}

This Java solution effectively addresses the problem of distributing chocolate bars such that the minimum sweetness level among given parts is maximized, taking into consideration the number of parts (k + 1).

  • The function maxSweetnessDistribution takes two parameters:

    • int[] sweetnessLevels: an array of integers representing the sweetness of each chocolate piece.
    • int k: the number of parts less than the total desired parts, as the pieces will be divided into k + 1 parts.
  • The calculation for the minimum possible sweetness (low) is derived from the minimum value in the sweetnessLevels array.

  • The maximum possible sweetness (high) is calculated by averaging the sum of all the sweet values in the sweetnessLevels over k + 1.

  • Use a binary search technique to find the highest minimum sweetness possible:

    1. Determine the middle point sweetness between low and high.
    2. Count how many groups can be formed where each group has a sweetness at least equal to the middle sweetness.
    3. If the number of groups formed is at least equal to peopleCount, adjust the low to middle.
    4. Otherwise, decrease high to middle - 1.
  • The loop continues until low is less than high, gradually refining the possible richest minimum sweetness that can be distributed equally among k + 1 persons.

  • Finally, the function returns the value of high, which represents the maximum possible minimum sweetness that can be achieved for the most equitable distribution.

This solution leverages efficient binary search principles and performs the calculations by continually adjusting the search space based on the divisibility of the sweetness levels into the required number of parts.

js
var calculateMaxSweetness = function(sweets, divisions) {
    let personCount = divisions + 1;
    let minimum = Math.min(...sweets);
    let maximum = Math.floor(sweets.reduce((acc, cur) => acc + cur) / personCount);
    
    while (minimum < maximum) {
        const middle = Math.floor((minimum + maximum + 1) / 2);
        let currentSweetness = 0;
        let peopleCounted = 0;
        
        for (const sweet of sweets) {
            currentSweetness += sweet;
            if (currentSweetness >= middle) {
                peopleCounted += 1;
                currentSweetness = 0;
            }
        }
        
        if (peopleCounted >= personCount) {
            minimum = middle;
        } else {
            maximum = middle - 1;
        }
    }
    
    return maximum;
};

The solution presents a JavaScript function named calculateMaxSweetness which aims to distribute a list of sweetness values among a specified number of people such that everyone gets a maximum and roughly equal amount of sweets. The function utilizes a binary search algorithm to efficiently determine the optimal division of sweets.

The JavaScript function works as follows:

  1. The total number of persons is identified by adding one to the given number of divisions, acknowledging that the sweets need to be divided among these many individuals.
  2. Initialize minimum as the smallest value in the sweets array, recognizing the least amount of sweetness that could potentially be received if divided equally.
  3. Establish maximum by calculating the average sweetness per person after summing all the items in the sweets and dividing by personCount.
  4. Employ a binary search between minimum and maximum:
    • Calculate the middle value of current minimum and maximum.
    • Traverse through the sweets array, aggregating sweetness until it matches or exceeds the middle value, which might be a potential maximum sweetness per person. If reached, reset the accumulated sweetness and increment a count of persons who have received their share.
    • Adjust minimum or maximum based on whether the number of persons who can get at least the middle-value amount of sweetness meets or exceeds personCount. Increase minimum to shrink the search space if the current middle-value can be distributed to sufficient people, otherwise decrease maximum.
  5. The search terminates when minimum and maximum converge, resulting in maximum being the highest possible minimum sweetness each person can receive under optimal division.

This approach ensures that the solution is computationally efficient, handling the division even for large input data by leveraging the binary search paradigm. Moreover, it assures that every individual gets the fairest possible share of sweetness that the input constraints allow.

python
class Solution:
    def distributeChocolates(self, chocolates: List[int], k: int) -> int:
        num_people = k + 1
        low = min(chocolates)
        high = sum(chocolates) // num_people

        while low < high:
            mid = (low + high + 1) // 2
            current_sum = 0
            count_people = 0

            for choco in chocolates:
                current_sum += choco

                if current_sum >= mid:
                    count_people += 1
                    current_sum = 0

            if count_people >= num_people:
                low = mid
            else:
                high = mid - 1

        return high

In this Python solution, you find the maximum amount of chocolate that can be evenly distributed among a number of people so that each gets at least a certain amount k. The chocolate distribution is defined by a list where each element denotes a packaged amount of chocolates.

The solution involves following steps in a binary search manner:

  1. Define the number of required distributions by adding one to k to factor in all people.
  2. Set the lower boundary (low) as the minimum amount from the chocolate list and the upper boundary (high) as the total chocolate amount divided by the number of people (num_people).
  3. Use a binary search mechanism where:
    • The middle value (mid) is calculated. This value represents a potential maximum amount of chocolate a single person could receive if chocolates are distributed fairly.
    • Traverse through each chocolate packet in the list and keep adding to current_sum until it at least matches mid. Each time it does, increment a counter for people who have received their share (count_people).
  4. Adjust the low and high boundaries based on whether the number of people who got their share is at least as much as the number of people you need to distribute to.
  5. Continue adjusting the boundaries until low is less than high.

The function returns the value of high which indicates the maximum minimum amount of chocolates that can be distributed to all people such that no one receives less than this number. This value ensures a fair distribution among the receivers ensuring that the number of people who at least get k amounts of chocolate is maximized within the given constraints.

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