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What is the factorial of 20?
20! = 20 x 19 x 18 x 17 x 16 x 15 x 14 x 13 x 12 x 11 x 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1 = 2432902008176640000
What is factorial of 20?
20! = 20 x 19 x 18 x 17 x 16 x 15 x 14 x 13 x 12 x 11 x 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1 = 2432902008176640000
How many different peptides can be formed by using all amino acids only once?
The number of different peptides that can be formed by using all 20 standard amino acids exactly once is 20 factorial, denoted as 20!. This calculates to approximately 2.43 x 10^18 unique peptides. Each peptide in this collection would have a distinct sequence of the 20 amino acids arranged in a specific order.
Write a c plus plus program that would accept a positive number and then output its factorial recall that the factorial of 0 is 1?
The factorial of 0 is indeed 1, but that's not really a problem. The problem is that the factorial of 20 is 2,432,902,008,176,640,000 and that's the largest factorial that will fit in a 64-bit integer. With only 21 factorials (including 0) to play with, a simple lookup table would be a lot quicker than calculating each of them separately. unsigned __int64 factorial(unsigned num) { switch (num) { case (0): case (1): return 1; case (2): return 2; case (3): return 6; case (4): return 24; case (5): return 120; //.... case (20): return 2432902008176640000; } return 0; // indicates error! } To calculate them individually, use the following function: unsigned __int64 factorial (unsigned num) { if (20<num) return 0; // indicates error! unsigned __int64 result= 1; while (1<num) result *= num--; return result; } To accommodate factorials greater than 20 you could use a 64-bit double-precision float, however the results will be an approximation rather than precise and the risk of overflowing still exists. The best solution is to employ a user-defined, dynamically-sized type specifically designed to cater for large integrals (although they'd no longer be integral, of course). There are many libraries available to cater for this but, personally, I use the GMP library as it's one of the fastest available.
