[코딩테스트] Persistent Bugger

Persistent BuggerWrite a function, persistence, that takes in a positive parameter num and returns its multiplicative persistence , which is the number of times you must multiply the digits in num until you reach a single digit.Examples :* persistence(39) == 3 // because 3*9 = 27, 2*7 = 14, 1*4=4* // and 4 has only one digit* persistence(999) == 4 // because 9*9*9 = 729, 7*2*9 = 126,* // 1*2*6 = 12, and finally 1*2 = 2* persistence(4) == 0 // because 4 is already a one-digit number→ 주어진 숫자의 각 자릿수 값을 곱해서 한자리..........

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