Saturday, December 9, 2023

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 {

    public int waysToSplitArray(int[] nums) {

        if (nums == null || nums.length <= 1 ) return 0;

        int sumSoFar = 0;

        int total = 0;

        int count = 0;

        for (int i = 0; i < nums.length; i++) {

            total += nums[i];

        }

 

        for (int i = 0; i < nums.length - 1; i++) {

            sumSoFar += nums[i];

            if (sumSoFar >= total-sumSoFar) {

                count += 1;

            }

        }

        return count;

    }

}

 

Test  cases:

[0] => 0

[1] => 0

[0,1] => 0

[1,0] => 1

[0,0,1] => 0

[0,1,0] => 1

[0,1,1] => 1

[1,0,0] => 2

[1,0,1] => 2

[1,1,0] => 2

[1,1,1] => 1

 

 

 

 

 

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