Given two numbers, fact and n, find the largest power of n that divides fact! (Factorial of fact).
Input : fact = 5, n = 2 Output : 3 Value of 5! is 120. The largest power of 2 that divides 120 is 8 (or 23 Input : fact = 146, n = 15 Output : 35
The idea is based on Legendre’s formula which finds largest power of a prime number that divides fact!. We find all prime factors of n. For every prime factor we find largest power of it that divides fact!. Finally we return minimum of all found powers.
fact = 146, n=15 First find the prime factor of 15 that are 3 and 5 then first divide with 3 and add i.e. Applying Legendre’s formula for prime factor 3. [146/3]+[48/3]+[16/3]+[5/3]+[1/3] = 70 48 + 16 + 5 + 1 + 0 = 70 There is 70 is maximum power of 3 prime number. 146! is divisible by 3^70 which is maximum. Applying Legendre’s formula for prime factor 5. [146/5]+[29/5]+[5/5]+[1/5] = 35 29 + 5 + 1 + 0 = 35 There is 35 is maximum power of 5 prime number.
Minimum of two powers is 35 which is our answer.
Note : If multiple powers of a prime factor are present in n, then we divide the count to get the maximum power value for this factor.
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