Flipping Coins

#include <bits/stdc++.h>
using namespace std;
long double p[401][401];
int main() {
  int n, k;
  cin >> n >> k;
  p[0][0] = 1.0;
  for(int i=0;i<k;i++) {
    for(int j=0;j<=n;j++) {
      if(j == 0) {
        p[i+1][j+1] += 0.5*p[i][j];
        p[i+1][j] += 0.5*p[i][j];
      } else if (j == n) {
        p[i+1][j-1] += 0.5*p[i][j];
        p[i+1][j] += 0.5*p[i][j];
      } else {
        p[i+1][j] += 0.5*p[i][j];
        p[i+1][j+1] += 0.5*p[i][j];
      }
    }
  }
  long double r = 0.0;
  for(int i=0;i<=n;i++) {
    r += i * p[k][i];
  }
  cout << setprecision(20) << fixed << r << endl;
  return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED