# Your task is to complete a function “count_heads()” that takes two inputs N and R. The function should return the probability of getting exactly R heads on N successive tosses of a fair coin. A fair coin has equal probability of landing a head or a tail (i. e. 0.5) on each toss.

Function “count_heads()” that takes two inputs N and R. the function should return the probability of getting exactly R heads on N successive tosses of a fair coin. A fair coin has equal probability of loading a head or a tail( i.e 0.5) on each toss

Contents

**Explanation**

Probability of getting K heads in N coin tosses

Given two integers N and R. The task is to calculate the probability of getting exactly r heads in n successive tosses.

A fair coin has an equal probability of landing a head or a tail on each toss.

Examples:

Input : N = 1, R = 1

Output : 0.500000

Input : N = 4, R = 3

Output : 0.250000

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Explanation:

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Given two integers N and R. The task is to calculate the probability of getting exactly r heads in n successive tosses.

A fair coin has an equal probability of landing a head or a tail on each toss.

include <bits/stdc++.h>

using namespace std;

// function to calculate factorial

int fact(int n)

{

int res = 1;

for (int i = 2; i <= n; i++)

res = res * i;

return res;

}

// apply the formula

double count_heads(int n, int r)

{

double output;

output = fact(n) / (fact(r) * fact(n – r));

output = output / (pow(2, n));

return output;

}

// Driver function

int main()

{

int n = 4, r = 3;

// call count_heads with n and r

cout << count_heads(n, r);

return 0;

}

Output:

0.250000

hope it help u

Probability of getting K heads in N coin tosses

Given two integers N and R. The task is to calculate the probability of getting exactly r heads in n successive tosses.

A fair coin has an equal probability of landing a head or a tail on each toss.

Examples:

Input : N = 1, R = 1

Output : 0.500000

Input : N = 4, R = 3

Output : 0.250000