# 2270. Number of Ways to Split Array

## Description

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

## Solutions

• class Solution {
public int waysToSplitArray(int[] nums) {
long s = 0;
for (int v : nums) {
s += v;
}
int ans = 0;
long t = 0;
for (int i = 0; i < nums.length - 1; ++i) {
t += nums[i];
if (t >= s - t) {
++ans;
}
}
return ans;
}
}

• class Solution {
public:
int waysToSplitArray(vector<int>& nums) {
long long s = accumulate(nums.begin(), nums.end(), 0ll);
long long t = 0;
int ans = 0;
for (int i = 0; i < nums.size() - 1; ++i) {
t += nums[i];
ans += t >= s - t;
}
return ans;
}
};

• class Solution:
def waysToSplitArray(self, nums: List[int]) -> int:
s = sum(nums)
ans = t = 0
for v in nums[:-1]:
t += v
if t >= s - t:
ans += 1
return ans


• func waysToSplitArray(nums []int) int {
s := 0
for _, v := range nums {
s += v
}
ans, t := 0, 0
for _, v := range nums[:len(nums)-1] {
t += v
if t >= s-t {
ans++
}
}
return ans
}