Queries to print count of distinct array elements after replacing element at index P by a given element
Given an array arr[] consisting of N integers and 2D array queries[][] consisting of Q queries of the form {p, x}, the task for each query is to replace the element at position p with x and print the count of distinct elements present in the array.
Examples:
Input: Q = 3, arr[] = {2, 2, 5, 5, 4, 6, 3}, queries[][] = {{1, 7}, {6, 8}, {7, 2}}
Output: {6, 6, 5}
Explanation:
The total distinct elements after each query (one-based indexing):
Query 1: p = 1 and x = 7. Therefore, arr[1] = 7 and arr[] becomes {7, 2, 5, 5, 4, 6, 3}. Hence, distinct elements = 6.
Query 2: p = 6 and x = 8. Therefore, arr[6] = 8 and arr[] becomes {7, 2, 5, 5, 4, 8, 3}. Hence, distinct elements = 6.
Query 3: p = 7 and x = 2. Therefore, arr[7] = 2 and arr[] becomes {7, 2, 5, 5, 4, 8, 2}. Hence, distinct elements = 5.Input: Q = 2, arr[] = {1, 1, 1, 1}, queries[][] = {{2, 2}, {3, 3}}
Output: {2, 3}
Explanation:
The total distinct elements after each query (one-based indexing):
Query 1: p = 2 and x = 2. Therefore, arr[2] = 2 and arr[] becomes {1, 2, 1, 1}. Hence, distinct elements = 2.
Query 2: p = 3 and x = 3. Therefore, arr[3] = 3 and arr[] becomes {1, 2, 3, 1}. Hence, distinct elements = 3.
Naive approach: The simplest approach is to update the given array for each query and insert all the elements of the updated array into a Set. Print the size of the set as the count of distinct array elements.
Below is the implementation of the above approach:
C++
// C++ Program to implement// the above approach#include <bits/stdc++.h>using namespace std;#define R 3#define C 2// Function to the total // number of distinct elements // after each query updatevoid Distinct(int arr[], int n, int p, int x){ // Update the array arr[p - 1] = x; // Store distinct elements set<int> set; for (int i = 0; i < n; i++) { set.insert(arr[i]); } // Print the size cout << set.size() << " ";}// Function to print the count of// distinct elements for each queryvoid updateArray(int arr[], int n, int queries[R][C], int q){ // Traverse the query for (int i = 0; i < q; i++) { // Function Call to update // each query Distinct(arr, n, queries[i][0], queries[i][1]); }}// Driver Codeint main(){ // Given array arr[] int arr[] = {2, 2, 5, 5, 4, 6, 3}; int N = sizeof(arr) / sizeof(arr[0]); int Q = 3; // Given queries int queries[R][C] = {{1, 7}, {6, 8}, {7, 2}}; // Function Call updateArray(arr, N, queries, Q);}// This code is contributed by gauravrajput1 |
Java
// Java program for the above approachimport java.io.*;import java.util.*;class GFG { // Function to the total number // of distinct elements after each // query update static void Distinct(int arr[], int n, int p, int x) { // Update the array arr[p - 1] = x; // Store distinct elements Set<Integer> set = new HashSet<>(); for (int i = 0; i < n; i++) { set.add(arr[i]); } // Print the size System.out.print(set.size() + " "); } // Function to print the count of // distinct elements for each query static void updateArray( int arr[], int n, int queries[][], int q) { // Traverse the query for (int i = 0; i < q; i++) { // Function Call to update // each query Distinct(arr, n, queries[i][0], queries[i][1]); } } // Driver Code public static void main(String[] args) { // Given array arr[] int[] arr = { 2, 2, 5, 5, 4, 6, 3 }; int N = arr.length; int Q = 3; // Given queries int queries[][] = new int[][] { { 1, 7 }, { 6, 8 }, { 7, 2 } }; // Function Call updateArray(arr, N, queries, Q); }} |
Python3
# Python3 program for the# above approach# Function to the total number# of distinct elements after# each query updatedef Distinct(arr, n, p, x): # Update the array arr[p - 1] = x; # Store distinct elements s = set(); for i in range(n): s.add(arr[i]); # Print the size print(len(s), end = " ");# Function to print count # of distinct elements for # each querydef updateArray(arr, n, queries, q): # Traverse the query for i in range(0, q): # Function Call to update # each query Distinct(arr, n, queries[i][0], queries[i][1]);# Driver Codeif __name__ == '__main__': # Given array arr arr = [2, 2, 5, 5, 4, 6, 3]; N = len(arr); Q = 3; # Given queries queries = [[1, 7], [6, 8], [7, 2]]; # Function Call updateArray(arr, N, queries, Q);# This code is contributed by shikhasingrajput |
C#
// C# program for the // above approachusing System;using System.Collections.Generic;class GFG{// Function to the total number// of distinct elements after each// query updatestatic void Distinct(int []arr, int n, int p, int x){ // Update the array arr[p - 1] = x; // Store distinct elements HashSet<int> set = new HashSet<int>(); for (int i = 0; i < n; i++) { set.Add(arr[i]); } // Print the size Console.Write(set.Count + " ");}// Function to print the count of// distinct elements for each querystatic void updateArray(int []arr, int n, int [,]queries, int q){ // Traverse the query for (int i = 0; i < q; i++) { // Function Call to update // each query Distinct(arr, n, queries[i, 0], queries[i, 1]); }}// Driver Codepublic static void Main(String[] args){ // Given array []arr int[] arr = {2, 2, 5, 5, 4, 6, 3}; int N = arr.Length; int Q = 3; // Given queries int [,]queries = new int[,] {{1, 7}, {6, 8}, {7, 2}}; // Function Call updateArray(arr, N, queries, Q);}}// This code is contributed by gauravrajput1 |
Javascript
<script>// Javascript Program to implement// the above approachvar R = 3var C = 2;// Function to the total // number of distinct elements // after each query updatefunction Distinct(arr, n, p, x){ // Update the array arr[p - 1] = x; // Store distinct elements var set = new Set(); for (var i = 0; i < n; i++) { set.add(arr[i]); } // Print the size document.write( set.size + " ");}// Function to print the count of// distinct elements for each queryfunction updateArray(arr, n, queries, q){ // Traverse the query for (var i = 0; i < q; i++) { // Function Call to update // each query Distinct(arr, n, queries[i][0], queries[i][1]); }}// Driver Code// Given array arr[]var arr = [2, 2, 5, 5, 4, 6, 3];var N = arr.length;var Q = 3;// Given queriesvar queries = [[1, 7], [6, 8], [7, 2]];// Function CallupdateArray(arr, N, queries, Q);</script> |
Output
6 6 5
Time Complexity: O(Q*N)
Auxiliary Space: O(N)
Efficient Approach: To optimize the above approach, the idea is to store the frequency of each array element in a Map and then traverse each query and print the size of the map after each update. Follow the below steps to solve the problem:
- Store the frequency of each element in a Map M.
- For each query {p, x}, perform the following steps:
- Decrease the frequency of arr[p] by 1 in the Map M. If its frequency reduces to 0, remove that element from the Map.
- Update arr[p] = x and increment the frequency of x by 1 in the Map if it is already present. Otherwise, add element x in the Map setting its frequency as 1.
- For each query in the above steps, print the size of the Map as the count of the distinct array elements.
Below is the implementation of the above approach:
C++
// C++ Program to implement// the above approach#include <bits/stdc++.h>using namespace std;#define Q 3// Function to store the frequency// of each element in the Mapvoid store(int arr[], int n, map<int, int> &map){ for (int i = 0; i < n; i++) { // Store the frequency of // element arr[i] map[arr[i]]++; }}// Function to update an array // and map & to find the // distinct elementsvoid Distinct(int arr[], int n, int p, int x, map<int, int> &map){ // Decrease the element // if it was previously // present in Map map[arr[p - 1]] = map[arr[p - 1]] - 1; if (map[arr[p - 1]] == 0) map.erase(arr[p - 1]); // Add the new element // to map map[x]++; // Update the array arr[p - 1] = x; // Print the count of // distinct elements cout << (map.size()) << " ";}// Function to count the distinct// element after updating each querystatic void updateQuery(int arr[], int n, int queries[Q][2], int q){ // Store the elements in map map<int,int> map; store(arr, n, map); for (int i = 0; i < q; i++) { // Function Call Distinct(arr, n, queries[i][0], queries[i][1], map); }}// Driver Codeint main(){ // Given array arr[] int arr[] = {2, 2, 5, 5, 4, 6, 3}; int N = sizeof(arr) / sizeof(arr[0]); // Given Queries int queries[Q][2] = {{1, 7}, {6, 8}, {7, 2}}; // Function Call updateQuery(arr, N, queries, Q);}// This code is contributed by gauravrajput1 |
Java
// Java program for the above approachimport java.io.*;import java.util.*;class GFG { // Function to store the frequency // of each element in the Map static void store(int arr[], int n, HashMap<Integer, Integer> map) { for (int i = 0; i < n; i++) { // Store the frequency of // element arr[i] if (!map.containsKey(arr[i])) map.put(arr[i], 1); else map.put(arr[i], map.get(arr[i]) + 1); } } // Function to update an array and // map & to find the distinct elements static void Distinct(int arr[], int n, int p, int x, HashMap<Integer, Integer> map) { // Decrease the element if it // was previously present in Map map.put(arr[p - 1], map.get(arr[p - 1]) - 1); if (map.get(arr[p - 1]) == 0) map.remove(arr[p - 1]); // Add the new element to map if (!map.containsKey(x)) { map.put(x, 1); } else { map.put(x, map.get(x) + 1); } // Update the array arr[p - 1] = x; // Print the count of distinct // elements System.out.print(map.size() + " "); } // Function to count the distinct // element after updating each query static void updateQuery( int arr[], int n, int queries[][], int q) { // Store the elements in map HashMap<Integer, Integer> map = new HashMap<>(); store(arr, n, map); for (int i = 0; i < q; i++) { // Function Call Distinct(arr, n, queries[i][0], queries[i][1], map); } } // Driver Code public static void main(String[] args) { // Given array arr[] int[] arr = { 2, 2, 5, 5, 4, 6, 3 }; int N = arr.length; int Q = 3; // Given Queries int queries[][] = new int[][] { { 1, 7 }, { 6, 8 }, { 7, 2 } }; // Function Call updateQuery(arr, N, queries, Q); }} |
Python3
# Python3 Program to implement# the above approach# Function to store the frequency# of each element in the Mapdef store(arr, n, Map) : for i in range(n) : # Store the frequency of # element arr[i] if (arr[i] not in Map) : Map[arr[i]] = 1 else : Map[arr[i]] += 1 # Function to update an array and# map & to find the distinct elementsdef Distinct(arr, n, p, x, Map) : # Decrease the element if it # was previously present in Map Map[arr[p - 1]] = Map[arr[p - 1]] - 1 if (Map[arr[p - 1]] == 0) : del Map[arr[p - 1]] # Add the new element to map if(x not in Map) : Map[x] = 1 else : Map[x] += 1 # Update the array arr[p - 1] = x # Print the count of distinct # elements print(len(Map), end = " ") # Function to count the distinct# element after updating each querydef updateQuery(arr, n, queries, q) : # Store the elements in map Map = {} store(arr, n, Map) for i in range(q) : # Function Call Distinct(arr, n, queries[i][0], queries[i][1], Map)# Given array []arrarr = [ 2, 2, 5, 5, 4, 6, 3 ]N = len(arr)Q = 3# Given queriesqueries = [ [ 1, 7 ], [ 6, 8 ], [ 7, 2 ] ]# Function callupdateQuery(arr, N, queries, Q)# This code is contributed by divyesh072019. |
C#
// C# program for the above approachusing System;using System.Collections.Generic;class GFG{// Function to store the frequency// of each element in the Mapstatic void store(int []arr, int n, Dictionary<int, int>map){ for(int i = 0; i < n; i++) { // Store the frequency of // element arr[i] if (!map.ContainsKey(arr[i])) map.Add(arr[i], 1); else map[arr[i]] = map[arr[i]] + 1; }}// Function to update an array and// map & to find the distinct elementsstatic void Distinct(int []arr, int n, int p, int x, Dictionary<int, int>map){ // Decrease the element if it // was previously present in Map map[arr[p - 1]] = map[arr[p - 1]] - 1; if (map[arr[p - 1]] == 0) map.Remove(arr[p - 1]); // Add the new element to map if (!map.ContainsKey(x)) { map.Add(x, 1); } else { map[x]= map[x] + 1; } // Update the array arr[p - 1] = x; // Print the count of distinct // elements Console.Write(map.Count + " ");}// Function to count the distinct// element after updating each querystatic void updateQuery(int []arr, int n, int [,]queries, int q){ // Store the elements in map Dictionary<int, int> map = new Dictionary<int, int>(); store(arr, n, map); for(int i = 0; i < q; i++) { // Function Call Distinct(arr, n, queries[i, 0], queries[i, 1], map); }}// Driver Codepublic static void Main(String[] args){ // Given array []arr int[] arr = { 2, 2, 5, 5, 4, 6, 3 }; int N = arr.Length; int Q = 3; // Given queries int [,]queries = new int[,]{ { 1, 7 }, { 6, 8 }, { 7, 2 } }; // Function call updateQuery(arr, N, queries, Q);}}// This code is contributed by Amit Katiyar |
Javascript
<script>// Javascript program for the above approach// Function to store the frequency // of each element in the Mapfunction store(arr,n,map){ for (let i = 0; i < n; i++) { // Store the frequency of // element arr[i] if (!map.has(arr[i])) map.set(arr[i], 1); else map.set(arr[i], map.get(arr[i]) + 1); }} // Function to update an array and // map & to find the distinct elementsfunction Distinct(arr,n,p,x,map){ // Decrease the element if it // was previously present in Map map.set(arr[p - 1], map.get(arr[p - 1]) - 1); if (map.get(arr[p - 1]) == 0) map.delete(arr[p - 1]); // Add the new element to map if (!map.has(x)) { map.set(x, 1); } else { map.set(x, map.get(x) + 1); } // Update the array arr[p - 1] = x; // Print the count of distinct // elements document.write(map.size + " ");}// Function to count the distinct // element after updating each queryfunction updateQuery(arr,n,queries,q){ // Store the elements in map let map = new Map(); store(arr, n, map); for (let i = 0; i < q; i++) { // Function Call Distinct(arr, n, queries[i][0], queries[i][1], map); }}// Driver Codelet arr=[2, 2, 5, 5, 4, 6, 3];let N = arr.length;let Q = 3;let queries=[[ 1, 7 ],[ 6, 8 ],[ 7, 2 ]];// Function CallupdateQuery(arr, N, queries, Q);// This code is contributed by patel2127</script> |
Output
6 6 5
Time Complexity: O(N + Q)
Auxiliary Space: O(N)
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