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Abhishek Chaudhary

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Number of Ways to Split Array

You are given a 0-indexed integer array `nums` of length `n`.

`nums` contains a valid split at index `i` if the following are true:

• The sum of the first `i + 1` elements is greater than or equal to the sum of the last `n - i - 1` elements.
• There is at least one element to the right of `i`. That is, `0 <= i < n - 1`.

Return the number of valid splits in `nums`.

Example 1:

Input: nums = [10,4,-8,7]
Output: 2
Explanation:
There are three ways of splitting nums into two non-empty parts:

• Split nums at index 0. Then, the first part is [10], and its sum is 10. The second part is [4,-8,7], and its sum is 3. Since 10 >= 3, i = 0 is a valid split.
• Split nums at index 1. Then, the first part is [10,4], and its sum is 14. The second part is [-8,7], and its sum is -1. Since 14 >= -1, i = 1 is a valid split.
• Split nums at index 2. Then, the first part is [10,4,-8], and its sum is 6. The second part is [7], and its sum is 7. Since 6 < 7, i = 2 is not a valid split. Thus, the number of valid splits in nums is 2.

Example 2:

Input: nums = [2,3,1,0]
Output: 2
Explanation:
There are two valid splits in nums:

• Split nums at index 1. Then, the first part is [2,3], and its sum is 5. The second part is [1,0], and its sum is 1. Since 5 >= 1, i = 1 is a valid split.
• Split nums at index 2. Then, the first part is [2,3,1], and its sum is 6. The second part is [0], and its sum is 0. Since 6 >= 0, i = 2 is a valid split.

Constraints:

• `2 <= nums.length <= 105`
• `-105 <= nums[i] <= 105`

SOLUTION:

``````class Solution:
def waysToSplitArray(self, nums: List[int]) -> int:
n = len(nums)
p = [0]
for num in nums:
p.append(p[-1] + num)
ctr = 0
for i in range(n - 1):
l = p[i + 1]
r = p[-1] - l
if l >= r:
ctr += 1
return ctr
``````