main.go

// Source: https://leetcode.com/problems/number-of-ways-to-split-array
// Title: Number of Ways to Split Array
// Difficulty: Medium
// Author: Mu Yang <http://muyang.pro>

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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 <= 10^5`
// - `-10^5 <= nums[i] <= 10^5`
//
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package main

func waysToSplitArray(nums []int) int {
	left := 0
	right := 0
	for _, num := range nums {
		right += num
	}

	n := len(nums)
	count := 0
	for _, num := range nums[:n-1] {
		left += num
		right -= num
		if left >= right {
			count++
		}
	}

	return count
}