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2324. Find Triangular Sum Of An Array

Array Math Simulation Combinatorics

Problem - Find Triangular Sum Of An Array

Medium

You are given a 0-indexed integer array nums, where nums[i] is a digit between 0 and 9 (inclusive).

The triangular sum of nums is the value of the only element present in nums after the following process terminates:

  1. Let nums comprise of n elements. If n == 1, end the process. Otherwise, create a new 0-indexed integer array newNums of length n - 1.
  2. For each index i, where 0 <= i < n - 1, assign the value of newNums[i] as (nums[i] + nums[i+1]) % 10, where % denotes modulo operator.
  3. Replace the array nums with newNums.
  4. Repeat the entire process starting from step 1.

Return the triangular sum of nums.

 

Example 1:

Input: nums = [1,2,3,4,5]
Output: 8
Explanation:
The above diagram depicts the process from which we obtain the triangular sum of the array.

Example 2:

Input: nums = [5]
Output: 5
Explanation:
Since there is only one element in nums, the triangular sum is the value of that element itself.

 

Constraints:

  • 1 <= nums.length <= 1000
  • 0 <= nums[i] <= 9

Solutions

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class Solution:
    def triangularSum(self, nums: List[int]) -> int:
        # n = len(nums)
        # sums = [[0] * (n - i) for i in range(n)]

        # for j in range(n):
        #     sums[0][j] = nums[j]

        # for i in range(1, n):
        #     for j in range(n - i):
        #         sums[i][j] = sums[i - 1][j] + sums[i - 1][j + 1]

        # return sums[-1][-1] % 10

        result = 0
        n = len(nums)
        for i, num in enumerate(nums):
            result += num * comb(n - 1, i)

        return result % 10

Submission Stats:

  • Runtime: 424 ms (91.67%)
  • Memory: 17.8 MB (95.36%)