Need help in Problem C of AtCoder Beginner Contest 126

Revision en2, by haribhatt34, 2019-05-19 16:51:35

My Solution -

#include <bits/stdc++.h>
using namespace std;

map<int, int> mp;

int findPower(int i, int k)
{
int t = i, cnt = 0;
while (t <= k)
{
if (mp.find(t) != mp.end())
{
cnt += mp[t];
break;
}
t *= 2;
++cnt;
}
return mp[i] = cnt;
}

int main()
{
int n, k;
cin >> n >> k;
// power of 2
vector<int> p2(31);
p2 = 1;
for (int i=1; i<p2.size(); ++i)	p2[i] = p2[i-1] * 2;

long double b = 0.0;
for (int i=n; i>=1; --i)
{
int p = findPower(i, k);
p = p2[p];
b += (long double)1/p;
}
cout << ((long double)1/n) * b << '\n';
return 0;
}


I know my solution is unnecessarily long, I was trying to catch value, so to use them later. I don't know what I am doing wrong, moreover I am not getting correct decimal precision. For sample — 100000 5, the output should be — 0.999973749998, but my program is returning 0.9999687500, why could it be?

#### History

Revisions Rev. Lang. By When Δ Comment
en3 haribhatt34 2019-05-19 16:52:18 4 Tiny change: 'bc126_c)\n[link to' -> 'bc126_c)\n\n[link to'
en2 haribhatt34 2019-05-19 16:51:35 3 Tiny change: 'lution -\n~~~~~\n#' -> 'lution -\n\n~~~~~\n#'
en1 haribhatt34 2019-05-19 16:50:52 1213 Initial revision (published)