Maximize total count from the given Array

Last Updated : 18 Sep, 2023

Given an array nums of length N which contains two types of numbers, one which has the value zero, the second which is a positive integer, the task is to collect numbers from the below operations and return the maximum value you can collect.

If the given number is a positive integer, then it’s your choice, whether you can put it on the top of the queue or not.
Else, if the number is zero, then pick the topmost number from the queue and remove it.

Examples:

Input: N = 7, nums = [1, 2, 3, 0, 4, 5, 0]
Output: 8
Explanation: To maximize the total value do the following operation while iterating the nums[ ]:
nums[0] = 1, put on the top of the queue. Queue becomes: [1]
nums[1] = 2, put on the top of the queue. Queue becomes: [2, 1]
nums[2] = 3, put on the top of the queue. Queue becomes: [3, 2, 1]
nums[3] = 0, pick the top value from the queue and remove it. Total val = 3, and queue becomes: [2, 1]
nums[4] = 4, put on the top of the queue. Queue becomes: [4, 2, 1]
nums[5] = 5, put on the top of the queue. Queue becomes: [5, 4, 2, 1]
nums[6] = 0, pick the top value from the queue and remove it. Total val = 3 + 5 = 8, and queue becomes: [4, 2, 1]
Return val = 8.

Input: N = 8, nums = [5, 1, 2, 0, 0, 4, 3, 0]
Output: 11
Explanation: To maximize the total value do the following operation while iterating the nums[ ]:
nums[0] = 5, put on the top of the queue. Queue becomes: [5]
nums[1] = 1, ignore this number. Queue remains: [5]
nums[2] = 2, put on the top of the queue. Queue becomes: [2, 5]
nums[3] = 0, pick the top value from the queue and remove it. Total val = 0 + 2 = 2, and queue becomes: [5]
nums[4] = 0, pick the top value from the queue and remove it. Total val = 2 + 5 = 7, and queue becomes: [ ]
nums[5] = 4, put on the top of the queue. Queue becomes: [4]
nums[6] = 3, ignore this number. Queue remains: [4]
nums[7] = 0, pick the top value from the queue and remove it. Total val = 7 + 4 = 11, and queue becomes: [ ]
Return val = 11.

Approach: To solve the problem follow the below idea:

We will use a decreasing priority queue and store the positive integers in it, when we encounter zero we will take the peek() element (if it is not empty) from the priority queue and add it to the variable val.

Below are the steps for the above approach:

Initialize a decreasing priority queue.
Iterate the given array,
- If you encounter any positive integer, add it to the priority queue.
- Else, if you encounter a zero, check whether the priority queue is empty or not. If it is not empty, remove the top element from it and add it to the variable val which contains the current sum of the maximum value.
Return the final answer val.

Below is the code for the above approach:

C++

// C++ code for the above approach
 
#include <functional>
#include <iostream>
#include <queue>
#include <vector>
using namespace std;
 
// Function to calculate maximum value
int calculateMaxVal(vector<int>& nums, int N)
{
    priority_queue<int> decreasing;
 
    int val = 0;
    for (int i = 0; i < N; i++) {
        if (nums[i] == 0) {
            if (!decreasing.empty()) {
                val += (decreasing.top());
                decreasing.pop();
            }
        }
        else {
            decreasing.push(nums[i]);
        }
    }
 
    return val;
}
 
// Drivers code
int main()
{
 
    int N = 8;
    vector<int> nums = { 5, 1, 2, 0, 0, 4, 3, 0 };
 
    cout << "Maximum value is: " << calculateMaxVal(nums, N)
         << endl;
 
    return 0;
}

Java

// Java code for the above approach
 
import java.util.*;
 
class GFG {
 
    // Drivers code
    public static void main(String[] args)
    {
        int N = 8;
        int[] nums = { 5, 1, 2, 0, 0, 4, 3, 0 };
        System.out.println("Maximum value is : "
                           + calculateMaxVal(nums, N));
    }
 
    // Function to calculate maximum value
    public static int calculateMaxVal(int[] nums, int N)
    {
        PriorityQueue<Integer> decreasing
            = new PriorityQueue<Integer>(
                Collections.reverseOrder());
        int val = 0;
        for (int i = 0; i < N; i++) {
            if (nums[i] == 0) {
                if (!decreasing.isEmpty())
                    val += decreasing.remove();
            }
            else {
                decreasing.add(nums[i]);
            }
        }
 
        return val;
    }
}

Python3

# Python code for the above approach:
 
import heapq
 
# Function to calculate maximum value
 
 
def calculateMaxVal(nums):
    decreasing = []
    val = 0
    for num in nums:
        if num == 0:
            if decreasing:
                val += -heapq.heappop(decreasing)
        else:
            heapq.heappush(decreasing, -num)
    return val
 
 
nums = [5, 1, 2, 0, 0, 4, 3, 0]
print("Maximum value is: ", calculateMaxVal(nums))
 
# This code is contributed by lokesh.

C#

// C# code for the above approach
 
using System;
using System.Collections.Generic;
 
class GFG {
    // Function to calculate maximum value
    static int CalculateMaxVal(List<int> nums, int N)
    {
        // Create a priority queue to store decreasing
        // numbers
        PriorityQueue<int> decreasing
            = new PriorityQueue<int>(new Comparison<int>(
                (x, y) => y.CompareTo(x)));
        int val = 0;
 
        // Iterate through the array
        for (int i = 0; i < N; i++) {
            // If the element is 0, pop the maximum element
            // from the priority queue and add it to the
            // result
            if (nums[i] == 0) {
                if (decreasing.Count > 0) {
                    val += decreasing.Dequeue();
                }
            }
            else {
                // If the element is non-zero, add it to the
                // priority queue
                decreasing.Enqueue(nums[i]);
            }
        }
 
        return val;
    }
 
    // Driver's code
    static void Main(string[] args)
    {
        // Input
        int N = 8;
        List<int> nums
            = new List<int>() { 5, 1, 2, 0, 0, 4, 3, 0 };
 
        // Function call
        Console.WriteLine("Maximum value is: "
                          + CalculateMaxVal(nums, N));
    }
}
 
// Implementation of a priority queue using a heap
public class PriorityQueue<T> {
    private List<T> _heap;
    private Comparison<T> _comparison;
 
    public PriorityQueue() { _heap = new List<T>(); }
 
    public PriorityQueue(Comparison<T> comparison)
    {
        _heap = new List<T>();
        _comparison = comparison;
    }
 
    public void Enqueue(T item)
    {
        _heap.Add(item);
        int i = _heap.Count - 1;
        while (i > 0) {
            int j = (i - 1) / 2;
            if (_comparison == null) {
                if (((IComparable<T>)_heap[j])
                        .CompareTo(item)
                    <= 0) {
                    break;
                }
            }
            else {
                if (_comparison(_heap[j], item) <= 0) {
                    break;
                }
            }
            _heap[i] = _heap[j];
            i = j;
        }
        _heap[i] = item;
    }
 
    public T Dequeue()
    {
        int lastIndex = _heap.Count - 1;
        T frontItem = _heap[0];
        _heap[0] = _heap[lastIndex];
        _heap.RemoveAt(lastIndex);
 
        --lastIndex;
        int i = 0;
        while (true) {
            int left = i * 2 + 1;
            if (left > lastIndex) {
                break;
            }
            int right = left + 1;
            if (right <= lastIndex
                && (_comparison == null
                        ? ((IComparable<T>)_heap[left])
                                  .CompareTo(_heap[right])
                              > 0
                        : _comparison(_heap[left],
                                      _heap[right])
                              > 0)) {
                left = right;
            }
            if (_comparison == null
                    ? ((IComparable<T>)_heap[i])
                              .CompareTo(_heap[left])
                          <= 0
                    : _comparison(_heap[i], _heap[left])
                          <= 0) {
                break;
            }
            T tmp = _heap[i];
            _heap[i] = _heap[left];
            _heap[left] = tmp;
            i = left;
        }
        return frontItem;
    }
 
    public int Count
    {
        get { return _heap.Count; }
    }
}

Javascript

// Function to calculate maximum value
function calculateMaxVal(nums) {
  let decreasing = [];
 
  let val = 0;
  for (let i = 0; i < nums.length; i++) {
    if (nums[i] === 0) {
      if (decreasing.length > 0) {
        val += decreasing[0];
        decreasing.shift();
      }
    } else {
      decreasing.push(nums[i]);
      decreasing.sort((a, b) => b - a);
    }
  }
 
  return val;
}
 
// Driver code
let nums = [5, 1, 2, 0, 0, 4, 3, 0];
console.log("Maximum value is: ", calculateMaxVal(nums));
// akashish__

Output

Maximum value is : 11

Time Complexity: O(N * log(N))
Auxiliary Space: O(N)

Approach 2: Greedy Algorithm

Initialize two variables include and exclude as 0, representing the maximum sum including and the excluding the current element, respectively.
Iterate through each element num in input array:
Calculate the new value of include as the sum of the exclude and num.
Update the value of exclude as the maximum of the include and exclude.
The final result will be the maximum of the include and exclude.

Implementation :

C++

#include <iostream>
#include <vector>
#include <algorithm>
 
int GFG(const std::vector<int>& arr) {
    int n = arr.size();
    if (n == 0) return 0;
    if (n == 1) return arr[0];
 
    std::vector<int> dp(n);
    dp[0] = arr[0];
    dp[1] = std::max(arr[0], arr[1]);
 
    for (int i = 2; i < n; i++) {
        dp[i] = std::max(dp[i - 1], dp[i - 2] + arr[i]);
    }
 
    return dp[n - 1];
}
 
int maximizeSumGreedy(const std::vector<int>& arr) {
    int include = 0, exclude = 0;
 
    for (int num : arr) {
        int new_include = exclude + num;
        exclude = std::max(include, exclude);
        include = new_include;
    }
 
    return std::max(include, exclude);
}
 
int main() {
    std::vector<int> inputArray = {1, 2, 5, 4, 5};
    int resultDP = GFG(inputArray);
    int resultGreedy = GFG(inputArray);
 
    std::cout << "Using Dynamic Programming:" << std::endl;
    std::cout << resultDP << std::endl;
 
    std::cout << "Using Greedy Algorithm:" << std::endl;
    std::cout << resultGreedy << std::endl;
 
    return 0;
}

Java

import java.util.List;
 
class Main {
    public static int GFG(List<Integer> arr) {
        int n = arr.size();
        if (n == 0)
            return 0;
        if (n == 1)
            return arr.get(0);
 
        int[] dp = new int[n];
        dp[0] = arr.get(0);
        dp[1] = Math.max(arr.get(0), arr.get(1));
 
        for (int i = 2; i < n; i++) {
            dp[i] = Math.max(dp[i - 1], dp[i - 2] + arr.get(i));
        }
 
        return dp[n - 1];
    }
 
    public static int maximizeSumGreedy(List<Integer> arr) {
        int include = 0, exclude = 0;
 
        for (int num : arr) {
            int new_include = exclude + num;
            exclude = Math.max(include, exclude);
            include = new_include;
        }
 
        return Math.max(include, exclude);
    }
 
    public static void main(String[] args) {
        List<Integer> inputArray = List.of(1, 2, 5, 4, 5);
        int resultDP = GFG(inputArray);
        int resultGreedy = GFG(inputArray);
 
        System.out.println("Using Dynamic Programming:");
        System.out.println(resultDP);
 
        System.out.println("Using Greedy Algorithm:");
        System.out.println(resultGreedy);
    }
}

Python3

# Python code for the above approach
 
# Function to Calculate the maximum sum using dynamic programming
def GFG(arr):
    n = len(arr)
    if n == 0:
        return 0
    if n == 1:
        return arr[0]
     
    # Initialize an array
    dp = [0] * n
    dp[0] = arr[0]
    dp[1] = max(arr[0], arr[1])
     
    # Traversing the loop and Calculating the maximum sum till index i
    for i in range(2, n):
        dp[i] = max(dp[i - 1], dp[i - 2] + arr[i])
 
    return dp[n - 1]
 
# Function to Calculate the maximum sum using the greedy approach
def maximizeSumGreedy(arr):
    # Initialize a variable to store the maximum sum including the current element
    include = 0
    # # Initialize a variable to store the maximum sum excluding the current element
    exclude = 0
     
    # Traverse the array and calculate the maximum sum using the greedy approach
    for num in arr:
        new_include = exclude + num
        exclude = max(include, exclude)
        include = new_include
 
    return max(include, exclude)
 
# Driver Code
if __name__ == "__main__":
    inputArray = [1, 2, 5, 4, 5]
    resultDP = GFG(inputArray)
    resultGreedy = maximizeSumGreedy(inputArray)
 
    print("Using Dynamic Programming:")
    print(resultDP)
 
    print("Using Greedy Algorithm:")
    print(resultGreedy)
     
# This code is contributed by Pushpesh Raj

C#

using System;
using System.Collections.Generic;
 
class Program
{
    // Function to find the maximum sum of a subsequence 
     // using Dynamic Programming
    static int GFG(List<int> arr)
    {
        int n = arr.Count;
        if (n == 0) return 0;
        if (n == 1) return arr[0];
        List<int> dp = new List<int>(n);
        dp.Add(arr[0]);
        dp.Add(Math.Max(arr[0], arr[1]));
        for (int i = 2; i < n; i++)
        {
            dp.Add(Math.Max(dp[i - 1], dp[i - 2] + arr[i]));
        }
        return dp[n - 1];
    }
    // Function to find the maximum sum of a subsequence 
     // using Greedy Algorithm
    static int MaximizeSumGreedy(List<int> arr)
    {
        int include = 0, exclude = 0;
        foreach (int num in arr)
        {
            int new_include = exclude + num;
            exclude = Math.Max(include, exclude);
            include = new_include;
        }
        return Math.Max(include, exclude);
    }
    static void Main()
    {
        List<int> inputArray = new List<int> { 1, 2, 5, 4, 5 };
        int resultDP = GFG(inputArray);
        int resultGreedy = MaximizeSumGreedy(inputArray);
        Console.WriteLine("Using Dynamic Programming:");
        Console.WriteLine(resultDP);
        Console.WriteLine("Using Greedy Algorithm:");
        Console.WriteLine(resultGreedy);
    }
}

Javascript

// Function to Calculate the maximum sum using dynamic programming
const GFG = (arr) => {
    const n = arr.length;
    if (n === 0) {
        return 0;
    }
    if (n === 1) {
        return arr[0];
    }
     
    // Initialize an array
    const dp = new Array(n).fill(0);
    dp[0] = arr[0];
    dp[1] = Math.max(arr[0], arr[1]);
     
    // Traversing the loop and Calculating the maximum sum till index i
    for (let i = 2; i < n; i++) {
        dp[i] = Math.max(dp[i - 1], dp[i - 2] + arr[i]);
    }
    return dp[n - 1];
};
 
// Function to Calculate the maximum sum using the greedy approach
const maximizeSumGreedy = (arr) => {
 
    // Initialize a variable to store the maximum sum including the current element
    let include = 0;
     
    // Initialize a variable to store the maximum sum excluding the current element
    let exclude = 0;
     
    // Traverse the array and calculate the maximum sum using the greedy approach    
    for (let num of arr) {
        const new_include = exclude + num;
        exclude = Math.max(include, exclude);
        include = new_include;
    }
    return Math.max(include, exclude);
};
 
 
// Driver Code
const inputArray = [1, 2, 5, 4, 5];
const resultDP = GFG(inputArray);
const resultGreedy = maximizeSumGreedy(inputArray);
console.log("Using Dynamic Programming:");
console.log(resultDP);
console.log("Using Greedy Algorithm:");
console.log(resultGreedy);

output :

Using Dynamic Programming:
11
Using Greedy Algorithm:
11

Suggest improvement

Maximize count of Decreasing Subsequences from the given Array

Share your thoughts in the comments

Maximize total count from the given Array

C++

Java

Python3

C#

Javascript

C++

Java

Python3

C#

Javascript

Please Login to comment...

Similar Reads

What kind of Experience do you want to share?