Intuition

A simple mathmatic relationship is that

\[total\_sum = left\_sum + right\_sum\]

Approach

• Initialize right_sum as total_sum, i.e, the sum of all elements in nums. Initialize left_sum as 0. Initialize res as 0 to represent the answer.
• Iterate through nums from 0 to n - 1.
  • At index i, subtract nums[i] from left_sum, and add nums[i] to right_sum.
  • Check if left_sum and right_sum satisfy the requirement, and update res accordingly.

Code

• Python3
• C++

• class Solution:
      def waysToSplitArray(self, nums: List[int]) -> int:
          left_sum = 0
          right_sum = sum(nums)
          res = 0
          for x in nums[:-1]:
              left_sum += x
              right_sum -= x
              if left_sum >= right_sum:
                  res += 1
          return res
  

• class Solution {
  public:
      int waysToSplitArray(vector<int>& nums) {
          long right_sum = 0, left_sum = 0;
          for (int x : nums) {
              right_sum += x;
          }
          int res = 0;
          for (int i = 0; i < nums.size() - 1; i++) {
              left_sum += nums[i];
              right_sum -= nums[i];
              if (left_sum >= right_sum) {
                  res++;
              }
          }
          return res;
      }
  };
  

Complexity

• Time complexity: $O(N)$
• Space complexity: $O(1)$