Given an array arr[] consisting of N positive integers and a 2D array Q[][] consisting of queries of the type {i, val}, the task for each query is to replace arr[i] by val and calculate the Bitwise AND of the modified array.
Examples:
Input: arr[] = {1, 2, 3, 4, 5}, Q[][] = {{0, 2}, {3, 3}, {4, 2}}
Output: 0 0 2
Explanation:
Query 1: Update A[0] to 2, then the array modifies to {2, 2, 3, 4, 5}. The Bitwise AND of all the elements is 0.
Query 2: Update A[3] to 3, then the array modifies to {2, 2, 3, 3, 5}. The Bitwise AND of all the elements is 0.
Query 3: Update A[4] to 2, then the modified array, A[]={2, 2, 3, 3, 2}. The Bitwise AND of all the elements is 2.Input: arr[] = {1, 2, 3}, Q[][] = {{1, 5}, {2, 4}}
Output: 1 0
Naive Approach: The simplest approach is to solve the given problem is to update the array element for each query and then find the bitwise AND of all the array elements by traversing the array in each query.
Time Complexity: O(N * Q)
Auxiliary Space: O(1)
Efficient Approach: The above approach can also be optimized by using an auxiliary array, say bitCount[][] of size 32 * N to store the sum of set bits at position i till the jth index of the array. So, bitCount[i][N – 1] represents the total sum of set bits at position i using all the array elements. Follow the steps below to solve the problem:
- Initialize an array bitCount[32][N] to store the set bits of the array elements.
- Iterate over the range [0, 31] using the variable i and perform the following steps:
- If the value of A[0] is set at the ith position, then update bitCount[i][0] to 1. Otherwise, update it to 0.
- Traverse the array A[] in the range [1, N – 1] using the variable j and perform the following steps:
- If the value of A[j] is set at ith position, then update bitCount[i][j] to 1.
- Add the value of bitCount[i][j – 1] to bitCount[i][j].
- Traverse the given array of queries Q[][] and perform the following steps:
- Initialize a variable, say res as 0, to store the result of the current query.
- Store the current value at the given index in currentVal and the new value in newVal.
- Iterate over the range [0, 31] using the variable i
- If newVal is set at index i and currentVal is not set, then increment prefix[i][N – 1] by 1.
- Otherwise, if currentVal is set at index i and newVal is not set, then decrement prefix[i][N – 1] by 1.
- If the value of prefix[i][N – 1] is equal to N, set this bit in res.
- After completing the above steps, print the value of res as the result.
Below is the implementation of the above approach:
C++
// C++ program for the above approach#include <bits/stdc++.h>using namespace std;// Store the number of set bits at// each positionint prefixCount[32][10000];// Function to precompute the prefix// count arrayvoid findPrefixCount(vector<int> arr, int size){ // Iterate over the range[0, 31] for (int i = 0; i < 32; i++) { // Set the bit at position i // if arr[0] is set at position i prefixCount[i][0] = ((arr[0] >> i) & 1); // Traverse the array and // take prefix sum for (int j = 1; j < size; j++) { // Update prefixCount[i][j] prefixCount[i][j] = ((arr[j] >> i) & 1); prefixCount[i][j] += prefixCount[i][j - 1]; } }}// Function to find the Bitwise AND// of all array elementsvoid arrayBitwiseAND(int size){ // Stores the required result int result = 0; // Iterate over the range [0, 31] for (int i = 0; i < 32; i++) { // Stores the number of set // bits at position i int temp = prefixCount[i] [size - 1]; // If temp is N, then set ith // position in the result if (temp == size) result = (result | (1 << i)); } // Print the result cout << result << " ";}// Function to update the prefix count// array in each queryvoid applyQuery(int currentVal, int newVal, int size){ // Iterate through all the bits // of the current number for (int i = 0; i < 32; i++) { // Store the bit at position // i in the current value and // the new value int bit1 = ((currentVal >> i) & 1); int bit2 = ((newVal >> i) & 1); // If bit2 is set and bit1 is // unset, then increase the // set bits at position i by 1 if (bit2 > 0 && bit1 == 0) prefixCount[i][size - 1]++; // If bit1 is set and bit2 is // unset, then decrease the // set bits at position i by 1 else if (bit1 > 0 && bit2 == 0) prefixCount[i][size - 1]--; }}// Function to find the bitwise AND// of the array after each queryvoid findbitwiseAND( vector<vector<int> > queries, vector<int> arr, int N, int M){ // Fill the prefix count array findPrefixCount(arr, N); // Traverse the queries for (int i = 0; i < M; i++) { // Store the index and // the new value int id = queries[i][0]; int newVal = queries[i][1]; // Store the current element // at the index int currentVal = arr[id]; // Update the array element arr[id] = newVal; // Apply the changes to the // prefix count array applyQuery(currentVal, newVal, N); // Print the bitwise AND of // the modified array arrayBitwiseAND(N); }}// Driver Codeint main(){ vector<int> arr{ 1, 2, 3, 4, 5 }; vector<vector<int> > queries{ { 0, 2 }, { 3, 3 }, { 4, 2 } }; int N = arr.size(); int M = queries.size(); findbitwiseAND(queries, arr, N, M); return 0;} |
Java
// Java program for the above approachimport java.io.*;import java.lang.*;import java.util.*;class GFG{// Store the number of set bits at// each positionstatic int prefixCount[][];// Function to precompute the prefix// count arraystatic void findPrefixCount(int arr[], int size){ // Iterate over the range[0, 31] for(int i = 0; i < 32; i++) { // Set the bit at position i // if arr[0] is set at position i prefixCount[i][0] = ((arr[0] >> i) & 1); // Traverse the array and // take prefix sum for(int j = 1; j < size; j++) { // Update prefixCount[i][j] prefixCount[i][j] = ((arr[j] >> i) & 1); prefixCount[i][j] += prefixCount[i][j - 1]; } }}// Function to find the Bitwise AND// of all array elementsstatic void arrayBitwiseAND(int size){ // Stores the required result int result = 0; // Iterate over the range [0, 31] for(int i = 0; i < 32; i++) { // Stores the number of set // bits at position i int temp = prefixCount[i][size - 1]; // If temp is N, then set ith // position in the result if (temp == size) result = (result | (1 << i)); } // Print the result System.out.print(result + " ");}// Function to update the prefix count// array in each querystatic void applyQuery(int currentVal, int newVal, int size){ // Iterate through all the bits // of the current number for(int i = 0; i < 32; i++) { // Store the bit at position // i in the current value and // the new value int bit1 = ((currentVal >> i) & 1); int bit2 = ((newVal >> i) & 1); // If bit2 is set and bit1 is // unset, then increase the // set bits at position i by 1 if (bit2 > 0 && bit1 == 0) prefixCount[i][size - 1]++; // If bit1 is set and bit2 is // unset, then decrease the // set bits at position i by 1 else if (bit1 > 0 && bit2 == 0) prefixCount[i][size - 1]--; }}// Function to find the bitwise AND// of the array after each querystatic void findbitwiseAND(int queries[][], int arr[], int N, int M){ prefixCount = new int[32][10000]; // Fill the prefix count array findPrefixCount(arr, N); // Traverse the queries for(int i = 0; i < M; i++) { // Store the index and // the new value int id = queries[i][0]; int newVal = queries[i][1]; // Store the current element // at the index int currentVal = arr[id]; // Update the array element arr[id] = newVal; // Apply the changes to the // prefix count array applyQuery(currentVal, newVal, N); // Print the bitwise AND of // the modified array arrayBitwiseAND(N); }}// Driver Codepublic static void main(String[] args){ int arr[] = { 1, 2, 3, 4, 5 }; int queries[][] = { { 0, 2 }, { 3, 3 }, { 4, 2 } }; int N = arr.length; int M = queries.length; findbitwiseAND(queries, arr, N, M);}}// This code is contributed by Kingash |
Python3
# Python3 program for the above approach# Store the number of set bits at# each positionprefixCount = [[0 for x in range(32)] for y in range(10000)]# Function to precompute the prefix# count arraydef findPrefixCount(arr, size): # Iterate over the range[0, 31] for i in range(32): # Set the bit at position i # if arr[0] is set at position i prefixCount[i][0] = ((arr[0] >> i) & 1) # Traverse the array and # take prefix sum for j in range(1, size): # Update prefixCount[i][j] prefixCount[i][j] = ((arr[j] >> i) & 1) prefixCount[i][j] += prefixCount[i][j - 1]# Function to find the Bitwise AND# of all array elementsdef arrayBitwiseAND(size): # Stores the required result result = 0 # Iterate over the range [0, 31] for i in range(32): # Stores the number of set # bits at position i temp = prefixCount[i][size - 1] # If temp is N, then set ith # position in the result if (temp == size): result = (result | (1 << i)) # Print the result print(result, end = " ")# Function to update the prefix count# array in each querydef applyQuery(currentVal, newVal, size): # Iterate through all the bits # of the current number for i in range(32): # Store the bit at position # i in the current value and # the new value bit1 = ((currentVal >> i) & 1) bit2 = ((newVal >> i) & 1) # If bit2 is set and bit1 is # unset, then increase the # set bits at position i by 1 if (bit2 > 0 and bit1 == 0): prefixCount[i][size - 1] += 1 # If bit1 is set and bit2 is # unset, then decrease the # set bits at position i by 1 elif (bit1 > 0 and bit2 == 0): prefixCount[i][size - 1] -= 1# Function to find the bitwise AND# of the array after each querydef findbitwiseAND(queries, arr, N, M): # Fill the prefix count array findPrefixCount(arr, N) # Traverse the queries for i in range(M): # Store the index and # the new value id = queries[i][0] newVal = queries[i][1] # Store the current element # at the index currentVal = arr[id] # Update the array element arr[id] = newVal # Apply the changes to the # prefix count array applyQuery(currentVal, newVal, N) # Print the bitwise AND of # the modified array arrayBitwiseAND(N)# Driver Codeif __name__ == "__main__": arr = [ 1, 2, 3, 4, 5 ] queries = [ [ 0, 2 ], [ 3, 3 ], [ 4, 2 ] ] N = len(arr) M = len(queries) findbitwiseAND(queries, arr, N, M)# This code is contributed by ukasp |
C#
// C# program for the above approachusing System;using System.Collections.Generic;class GFG{// Store the number of set bits at// each positionstatic int [,]prefixCount = new int[32, 10000];// Function to precompute the prefix// count arraystatic void findPrefixCount(List<int> arr, int size){ // Iterate over the range[0, 31] for(int i = 0; i < 32; i++) { // Set the bit at position i // if arr[0] is set at position i prefixCount[i, 0] = ((arr[0] >> i) & 1); // Traverse the array and // take prefix sum for(int j = 1; j < size; j++) { // Update prefixCount[i][j] prefixCount[i, j] = ((arr[j] >> i) & 1); prefixCount[i, j] += prefixCount[i, j - 1]; } }}// Function to find the Bitwise AND// of all array elementsstatic void arrayBitwiseAND(int size){ // Stores the required result int result = 0; // Iterate over the range [0, 31] for(int i = 0; i < 32; i++) { // Stores the number of set // bits at position i int temp = prefixCount[i, size - 1]; // If temp is N, then set ith // position in the result if (temp == size) result = (result | (1 << i)); } // Print the result Console.Write(result + " ");}// Function to update the prefix count// array in each querystatic void applyQuery(int currentVal, int newVal, int size){ // Iterate through all the bits // of the current number for(int i = 0; i < 32; i++) { // Store the bit at position // i in the current value and // the new value int bit1 = ((currentVal >> i) & 1); int bit2 = ((newVal >> i) & 1); // If bit2 is set and bit1 is // unset, then increase the // set bits at position i by 1 if (bit2 > 0 && bit1 == 0) prefixCount[i, size - 1]++; // If bit1 is set and bit2 is // unset, then decrease the // set bits at position i by 1 else if (bit1 > 0 && bit2 == 0) prefixCount[i, size - 1]--; }}// Function to find the bitwise AND// of the array after each querystatic void findbitwiseAND(int [,]queries, List<int> arr, int N, int M){ // Fill the prefix count array findPrefixCount(arr, N); // Traverse the queries for(int i = 0; i < M; i++) { // Store the index and // the new value int id = queries[i,0]; int newVal = queries[i,1]; // Store the current element // at the index int currentVal = arr[id]; // Update the array element arr[id] = newVal; // Apply the changes to the // prefix count array applyQuery(currentVal, newVal, N); // Print the bitwise AND of // the modified array arrayBitwiseAND(N); }}// Driver Codepublic static void Main(){ List<int> arr = new List<int>(){ 1, 2, 3, 4, 5 }; int [,] queries = new int [3, 2]{ { 0, 2 }, { 3, 3 }, { 4, 2 } }; int N = arr.Count; int M = 3; findbitwiseAND(queries, arr, N, M);}}// This code is contributed by ipg2016107 |
Javascript
<script>// JavaScript program to implement// the above approach// Store the number of set bits at// each positionlet prefixCount = [[]]; // Function to precompute the prefix// count arrayfunction findPrefixCount(arr, size){ // Iterate over the range[0, 31] for(let i = 0; i < 32; i++) { // Set the bit at position i // if arr[0] is set at position i prefixCount[i][0] = ((arr[0] >> i) & 1); // Traverse the array and // take prefix sum for(let j = 1; j < size; j++) { // Update prefixCount[i][j] prefixCount[i][j] = ((arr[j] >> i) & 1); prefixCount[i][j] += prefixCount[i][j - 1]; } }} // Function to find the Bitwise AND// of all array elementsfunction arrayBitwiseAND(size){ // Stores the required result let result = 0; // Iterate over the range [0, 31] for(let i = 0; i < 32; i++) { // Stores the number of set // bits at position i let temp = prefixCount[i][size - 1]; // If temp is N, then set ith // position in the result if (temp == size) result = (result | (1 << i)); } // Print the result document.write(result + " ");} // Function to update the prefix count// array in each queryfunction applyQuery(currentVal, newVal, size){ // Iterate through all the bits // of the current number for(let i = 0; i < 32; i++) { // Store the bit at position // i in the current value and // the new value let bit1 = ((currentVal >> i) & 1); let bit2 = ((newVal >> i) & 1); // If bit2 is set and bit1 is // unset, then increase the // set bits at position i by 1 if (bit2 > 0 && bit1 == 0) prefixCount[i][size - 1]++; // If bit1 is set and bit2 is // unset, then decrease the // set bits at position i by 1 else if (bit1 > 0 && bit2 == 0) prefixCount[i][size - 1]--; }} // Function to find the bitwise AND// of the array after each queryfunction findbitwiseAND(queries, arr, N, M){ prefixCount = new Array(32); // Loop to create 2D array using 1D array for (var i = 0; i < prefixCount.length; i++) { prefixCount[i] = new Array(2); } // Fill the prefix count array findPrefixCount(arr, N); // Traverse the queries for(let i = 0; i < M; i++) { // Store the index and // the new value let id = queries[i][0]; let newVal = queries[i][1]; // Store the current element // at the index let currentVal = arr[id]; // Update the array element arr[id] = newVal; // Apply the changes to the // prefix count array applyQuery(currentVal, newVal, N); // Print the bitwise AND of // the modified array arrayBitwiseAND(N); }}// Driver code let arr = [ 1, 2, 3, 4, 5 ]; let queries = [[ 0, 2 ], [ 3, 3 ], [ 4, 2 ]]; let N = arr.length; let M = queries.length; findbitwiseAND(queries, arr, N, M);// This code is contributed by code_hunt.</script> |
Output:
0 0 2
Time Complexity: O(N + M)
Auxiliary Space: O(N)
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