Problem Link :- GFG POTD
Problem statement
You are given an array of N elements and num queries, In each query you are given three numbers L,R and K and you have to tell, how many indexes are there in between L and R(L<=i<=R) such that the frequency of a[i] from index i to n-1 is k.
Note: 0-based indexing
Note: 0-based indexing
Significance of problem
The significance of this problem lies in its exploration of efficient frequency counting within a given array, providing insights into optimizing queries involving frequency checks. The code solution aims to address these queries by computing the frequency of each element in the array and subsequently handling user-defined range queries efficiently. By establishing a frequency array, the code streamlines the process of determining the occurrences of a specific element within the specified index range, contributing to a foundational understanding of array manipulation and frequency-based algorithms.
Furthermore, this problem serves as a practical exercise in implementing query-based algorithms, a common scenario in real-world applications like data analysis and database querying. The task involves handling multiple queries efficiently, a skill relevant in diverse computational domains where rapid retrieval and analysis of specific data subsets are crucial.
Additionally, the problem encourages learners to consider time and space complexities, fostering an appreciation for algorithmic efficiency. The code solution, while functional, demonstrates room for improvement, prompting learners to explore more optimized strategies for frequency computation and query processing.
In essence, mastering this problem equips developers with valuable skills in frequency-based algorithms, query optimization, and array manipulation—fundamental concepts applicable in various programming scenarios and essential for developing efficient solutions to real-world computational challenges.
Furthermore, this problem serves as a practical exercise in implementing query-based algorithms, a common scenario in real-world applications like data analysis and database querying. The task involves handling multiple queries efficiently, a skill relevant in diverse computational domains where rapid retrieval and analysis of specific data subsets are crucial.
Additionally, the problem encourages learners to consider time and space complexities, fostering an appreciation for algorithmic efficiency. The code solution, while functional, demonstrates room for improvement, prompting learners to explore more optimized strategies for frequency computation and query processing.
In essence, mastering this problem equips developers with valuable skills in frequency-based algorithms, query optimization, and array manipulation—fundamental concepts applicable in various programming scenarios and essential for developing efficient solutions to real-world computational challenges.
Easiest Explanation
Imagine you have a box with N different colored balls in it. The colors of the balls can be repeated, which means you can have more than one ball of the same color.
Now, someone gives you a set of questions (called "queries") to answer about the box and the balls inside it.
Each question has three parts:
L: This is the starting point of a range of balls you need to look at inside the box. It's like someone is pointing at a specific ball in the box and saying "start here".
R: This is the ending point of that same range of balls. It's like someone is pointing at another ball in the box and saying "stop here".
K: This is a number that tells you how many times a specific color of ball appears in the range of balls between L and R. The goal is to count how many times a ball with a specific color appears in a range of balls, but only if it appears exactly K times in the remaining part of the box (the part that comes after the range you're looking at).
For example, let's say you're given a range of balls from L to R that contains 10 balls, and K is 2. This means you need to count how many balls in that range appear twice in the remaining part of the box (after the 10th ball).
So, if you have a ball with the color "red" that appears twice in the remaining part of the box, and it also appears twice in the range of balls between L and R, then you would count that ball as one of the answers to the question.
I hope that explanation helps! If you find any difficulty in solving, feel free to comment with your doubts.
Now, someone gives you a set of questions (called "queries") to answer about the box and the balls inside it.
Each question has three parts:
L: This is the starting point of a range of balls you need to look at inside the box. It's like someone is pointing at a specific ball in the box and saying "start here".
R: This is the ending point of that same range of balls. It's like someone is pointing at another ball in the box and saying "stop here".
K: This is a number that tells you how many times a specific color of ball appears in the range of balls between L and R. The goal is to count how many times a ball with a specific color appears in a range of balls, but only if it appears exactly K times in the remaining part of the box (the part that comes after the range you're looking at).
For example, let's say you're given a range of balls from L to R that contains 10 balls, and K is 2. This means you need to count how many balls in that range appear twice in the remaining part of the box (after the 10th ball).
So, if you have a ball with the color "red" that appears twice in the remaining part of the box, and it also appears twice in the range of balls between L and R, then you would count that ball as one of the answers to the question.
I hope that explanation helps! If you find any difficulty in solving, feel free to comment with your doubts.
class Solution{ public: vector<int> solveQueries(int N, int num, vector<int> &arr, vector<vector<int>> &Q) { vector<int> freq(N,0); for(int i=0;i<N;i++) { int count=0; for(int j=i;j<N;j++) { if(arr[i]==arr[j]) count++; } freq[i]=count; } vector<int> ans; for(int i=0;i<num;i++) { int l=Q[i][0],r=Q[i][1],k=Q[i][2]; int count=0; for(int j=l;j<=r;j++) { if(freq[j]==k) count++; } ans.push_back(count); } return ans; } };
Here's how the function works:
1. The code defines a C++ function called solveQueries() which takes four arguments: N, num, arr, and Q.
2. N is an integer representing the size of the input array arr.
3. num is an integer representing the number of queries in the input vector Q.
4. arr is a reference to an integer vector containing the elements of the input array.
5. Q is a reference to a two-dimensional integer vector containing the queries. Each query is a vector of three integers: L, R, and K.
6. The code creates a new integer vector called freq with N elements, initialized to zero.
7. It then loops through each index i of the input array arr from 0 to N-1:
a. It initializes a variable count to zero.
b. It loops through each index j of the input array arr from i to N-1.
c. If the element at index i is equal to the element at index j, it increments count.
d. It then sets the value of freq[i] to count. This stores the number of times the element at index i appears in the subarray of arr from index i to the end of the array.
8. The code creates a new integer vector called ans.
9. It loops through each query in the input vector Q:
a. It initializes a variable count to zero.
b. It sets the variables l, r, and k to the first, second, and third elements of the current query, respectively.
c. It loops through each index j of the input array arr from l to r:
d. It appends the value of count to the ans vector.
10. The code returns the ans vector, which contains the number of indexes between L and R (inclusive) where the frequency of the corresponding element in the arr array from that index to the end of the array is equal to K.
2. N is an integer representing the size of the input array arr.
3. num is an integer representing the number of queries in the input vector Q.
4. arr is a reference to an integer vector containing the elements of the input array.
5. Q is a reference to a two-dimensional integer vector containing the queries. Each query is a vector of three integers: L, R, and K.
6. The code creates a new integer vector called freq with N elements, initialized to zero.
7. It then loops through each index i of the input array arr from 0 to N-1:
a. It initializes a variable count to zero.
b. It loops through each index j of the input array arr from i to N-1.
c. If the element at index i is equal to the element at index j, it increments count.
d. It then sets the value of freq[i] to count. This stores the number of times the element at index i appears in the subarray of arr from index i to the end of the array.
8. The code creates a new integer vector called ans.
9. It loops through each query in the input vector Q:
a. It initializes a variable count to zero.
b. It sets the variables l, r, and k to the first, second, and third elements of the current query, respectively.
c. It loops through each index j of the input array arr from l to r:
d. It appends the value of count to the ans vector.
10. The code returns the ans vector, which contains the number of indexes between L and R (inclusive) where the frequency of the corresponding element in the arr array from that index to the end of the array is equal to K.
Learning Outcomes
Solving the array frequency query problem yields crucial learning outcomes in various aspects of algorithmic thinking and data manipulation. Firstly, learners gain proficiency in frequency counting techniques, understanding how to efficiently compute the occurrences of elements within an array. This skill is fundamental in tasks involving data analysis and pattern recognition.
Secondly, the problem enhances expertise in handling range queries, a common scenario in databases and information retrieval systems. The code's implementation of user-defined queries offers practical insights into managing multiple queries effectively, a skill applicable across diverse programming domains.
Moreover, learners develop a nuanced understanding of time and space complexities. The code solution, though functional, prompts consideration of optimization strategies, encouraging a deeper exploration of efficient algorithms and data structures for frequency computations.
Additionally, the problem fosters a comprehension of array manipulation, laying the foundation for more advanced topics in data structure manipulation and algorithmic design. The iterative approach to computing frequencies and addressing queries contributes to a well-rounded skill set in algorithmic problem-solving.
Secondly, the problem enhances expertise in handling range queries, a common scenario in databases and information retrieval systems. The code's implementation of user-defined queries offers practical insights into managing multiple queries effectively, a skill applicable across diverse programming domains.
Moreover, learners develop a nuanced understanding of time and space complexities. The code solution, though functional, prompts consideration of optimization strategies, encouraging a deeper exploration of efficient algorithms and data structures for frequency computations.
Additionally, the problem fosters a comprehension of array manipulation, laying the foundation for more advanced topics in data structure manipulation and algorithmic design. The iterative approach to computing frequencies and addressing queries contributes to a well-rounded skill set in algorithmic problem-solving.
Conclusion
In conclusion, solving the array frequency query problem offers valuable insights into efficient frequency counting and query optimization. Learners gain proficiency in handling user-defined queries, an essential skill for real-world applications like data analysis. The problem deepens understanding of array manipulation and prompts consideration of time and space complexities.
Mastering this problem equips developers with fundamental skills in algorithmic thinking, fostering the ability to tackle diverse programming challenges by efficiently computing frequencies and addressing queries within an array.
Mastering this problem equips developers with fundamental skills in algorithmic thinking, fostering the ability to tackle diverse programming challenges by efficiently computing frequencies and addressing queries within an array.
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