2221. Find Triangular Sum of an Array

Description

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

Solution: Simulation

• Time complexity: O(n²)
• Space complexity: O(1)

 

JavaScript

/**
 * @param {number[]} nums
 * @return {number}
 */
const triangularSum = function (nums) {
  const n = nums.length;

  for (let operator = 1; operator < n; operator++) {
    for (let index = 0; index < n - operator; index++) {
      const sum = nums[index] + nums[index + 1];

      nums[index] = sum % 10;
    }
  }

  return nums[0];
};