Code providing wrong output for test case

#1

#include
using namespace std;

int countBits(int n)
{

int ans=0;

while(n>0)
{
	ans=ans+(n&1);
	n=n>>1;
}
return ans;

}

int main() {

int q,res=0;
cin>>q;
while(q--)
{
	int a,b,i;
	cin>>a>>b;
	for(i=a;i<=b;i++)
	{
		res=res+countBits(i);
	}
	cout<<res<<endl;
}
return 0;

}

For the test case 10,15 the output is coming as 18 instead of 17. I dry ran the code, but couldn’t find out the mistake.

#2

hi @pratyushnitdgp19_2c287088d77b5893
refer this code -->

#include<iostream>
using namespace std;
int main(){
	
	int t;
	cin>>t;
	
	int ans_arr[1000];
	
	for(int i=0;i<t;i++){
	
	int a,b;
	cin>>a>>b;
	
	int count = 0;
	for(int j=a;j<=b;j++){
		int num = j;
			
		while(num>0){
			int rem = num%2;
			if(rem == 1){
				count++;
			}
			num=num/2;
		}
	}
	ans_arr[i]=count;
	}
	
	for(int i=0;i<t;i++){
		cout<<ans_arr[i]<<endl;
	}
}
#3

Sir actually I was doing this problem under Bitmasking topic, so Sir I wanted to ask if this can be done using bitwise operators.

#4

ok… refer this–>

#include <iostream>
using namespace std;

int countSetBits(int n) {
	int res = 0;
	if (n == 1){
		return 1;
	} else {
		while (n > 0) {
		n = (n & (n - 1));
		res++;
		}
		return res;
	}
}

int main() {
	int t;
    cin>>t;
	while (t--) {
		int a, b, setBits = 0;
		cin >> a >> b;

		for (int i = a; i <= b; i++) {
			setBits += countSetBits(i);
		}

		cout << setBits <<endl;
	}
	return 0;
}
#5

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