C++ Code to Process Query Operation on Binary Array

Suppose we have an array A with n elements and another list of queries Q with q queries. each Query[i] contains a pair (x, k). When we process a query, for x: decrease the value of A[x] by 1. For k, print kth largest element. Initially all elements in A is either 0 or 1.

So, if the input is like A = [1, 1, 0, 1, 0]; Q = [[2, 3], [1, 2], [2, 3], [2, 1], [2, 5]], then the output will be [1, 1, 1, 0]

Steps

To solve this, we will follow these steps −

n := size of A
m := 0
for initialize i := 0, when i < n, update (increase i by 1), do:
   if A[i] is non-zero, then:
      (increase m by 1)
for initialize j := 0, when j < size of Q, update (increase j by 1),
do:
   x := Q[j, 0]
   k := Q[j, 1]
   if x is same as 0, then:
      if A[k] is non-zero, then:
         (decrease m by 1)
      Otherwise
         (increase m by 1)
      A[k] := A[k] XOR 1
   Otherwise
      if m >= k, then:
         print 1
      Otherwise
         print 0

Example

Let us see the following implementation to get better understanding −

#include <bits/stdc++.h>
using namespace std;
void solve(vector<int> A, vector<vector<int>> Q){
   int n = A.size();
   int m = 0;
   for (int i = 0; i < n; i++){
      if (A[i])
      m++;
   }
   for (int j = 0; j < Q.size(); j++){
      int x = Q[j][0];
      int k = Q[j][1];
      if (x == 0){
         if (A[k])
            m--;
         else
            m++;
         A[k] ^= 1;
      }
      else{
         if (m >= k)
            cout << 1 << ", ";
         else
            cout << 0 << ", ";
      }
   }
}
int main(){
   vector<int> A = { 1, 1, 0, 1, 0 };
   vector<vector<int>> Q = { { 1, 2 }, { 0, 1 }, { 1, 2 }, { 1, 0 },{ 1, 4 } };
   solve(A, Q);
}

Input

{ 1, 1, 0, 1, 0 }, { { 1, 2 }, { 0, 1 }, { 1, 2 }, { 1, 0 }, { 1, 4 }}

Output

1, 1, 1, 0,