2221. Find Triangular Sum of an Array.java

2221. Find Triangular Sum of an Array
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Medium
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Hint
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:

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.
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.
Replace the array nums with newNums.
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
class Solution {

    public int triangularSum(int[] nums) {
        List<Integer> current = Arrays.stream(nums)
            .boxed()
            .collect(Collectors.toList());
        while (current.size() > 1) {
            List<Integer> newNums = new ArrayList<>();
            for (int i = 0; i < current.size() - 1; ++i) {
                newNums.add((current.get(i) + current.get(i + 1)) % 10);
            }
            current = newNums;
        }
        return current.get(0);
    }
}