Subtract the Product and Sum of Digits of an Integer
- 时间:2020-09-15 16:10:27
- 分类:网络文摘
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Given an integer number n, return the difference between the product of its digits and the sum of its digits.
Example 1:
Input: n = 234
Output: 15
Explanation:
Product of digits = 2 * 3 * 4 = 24
Sum of digits = 2 + 3 + 4 = 9
Result = 24 – 9 = 15Example 2:
Input: n = 4421
Output: 21
Explanation:
Product of digits = 4 * 4 * 2 * 1 = 32
Sum of digits = 4 + 4 + 2 + 1 = 11
Result = 32 – 11 = 21Constraints:
1 <= n <= 10^5Hints:
How to compute all digits of the number?
Use modulus operator (%) to compute the last digit.
Generalise modulus operator idea to compute all digits.

leetcode-debugger
To get the digits of a integer, we can iteratedly divide the integer by ten, and retrieve the right-most digit by using modulous operator (%). The time complexity is O(lgN).
1 2 3 4 5 6 7 8 9 10 11 12 13 | class Solution { public: int subtractProductAndSum(int n) { int sum = 0; int product = 1; while (n > 0) { sum += n % 10; product *= n % 10; n /= 10; } return product - sum; } }; |
class Solution { public: int subtractProductAndSum(int n) { int sum = 0; int product = 1; while (n > 0) { sum += n % 10; product *= n % 10; n /= 10; } return product - sum; } };
The C++ code above requires O(1) constant space. And in Python, you could convert the integer into string, join them with a space, then split them into array of digit strings, finally convert them into list of digits by using the map function.
1 2 3 4 5 6 7 | from operator import mul from functools import reduce class Solution: def subtractProductAndSum(self, n: int) -> int: temp = list(map(int, ' '.join(str(n)).split())) return reduce(mul, temp, 1) - sum(temp) |
from operator import mul from functools import reduce class Solution: def subtractProductAndSum(self, n: int) -> int: temp = list(map(int, ' '.join(str(n)).split())) return reduce(mul, temp, 1) - sum(temp)
Then, we can compute the produce by using the reduce function, with the mul operator. The sum of digits can be just obtained via the sum() function.
–EOF (The Ultimate Computing & Technology Blog) —
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