Created
September 15, 2019 16:51
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Write 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.
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| function persistence(num, count = 0){ | |
| return num > 9 ? persistence(eval(`${num}`.split('').join('*')), count+1) : count; | |
| } | |
| 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 |
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