C++ Pascal三角與模10算術解Leetcode 2221 Find Triangular Sum of an Array(含Py3 Code)

C++ Pascal三角與模10算術解Leetcode 2221  Find Triangular Sum of an Array

如果採用有支援非常長int的程式語言，mod 10算術就整個省略，就用Pascal三角的性質，可得快速解

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If a programming language that supports very long ints is used, the mod 10 arithmetic can be omitted entirely, and the properties of Pascal's triangle can be used to obtain a fast solution.

[codes on Leetcode]https://leetcode.com/problems/find-triangular-sum-of-an-array/solutions/7234872/pascal-triangle-mod10-arithmetic-o-n-beats-100/

[Playlist for Number Theory, Primes etc]https://www.youtube.com/watch?v=3FUyGjH_FZ0&list=PLYRlUBnWnd5Ld53SovfXQROVMAI_La2dv

class Solution:
    def triangularSum(self, nums: List[int]) -> int:
        n=len(nums)-1
        ans, A=nums[0], 1
        for k in range(1, n+1):
            A=A*(n-k+1)//k
            ans=(ans+nums[k]*A)%10
        return ans