LeetCode-in-Java
1712. Ways to Split Array Into Three Subarrays
Medium
A split of an integer array is good if:
- The array is split into three non-empty contiguous subarrays - named
left,mid,rightrespectively from left to right. - The sum of the elements in
leftis less than or equal to the sum of the elements inmid, and the sum of the elements inmidis less than or equal to the sum of the elements inright.
Given nums, an array of non-negative integers, return the number of good ways to split nums. As the number may be too large, return it modulo 109 + 7.
Example 1:
Input: nums = [1,1,1]
Output: 1
Explanation: The only good way to split nums is [1] [1] [1].
Example 2:
Input: nums = [1,2,2,2,5,0]
Output: 3
Explanation: There are three good ways of splitting nums:
[1] [2] [2,2,5,0]
[1] [2,2] [2,5,0]
[1,2] [2,2] [5,0]
Example 3:
Input: nums = [3,2,1]
Output: 0
Explanation: There is no good way to split nums.
Constraints:
3 <= nums.length <= 1050 <= nums[i] <= 104
Solution
public class Solution {
public int waysToSplit(int[] nums) {
int sum = 0;
for (int num : nums) {
sum += num;
}
int cur = 0;
long res = 0;
int i = 0;
int idx1 = 1;
int sum1 = nums[0];
int idx2 = 1;
int sum2 = nums[0];
while (i < nums.length) {
cur += nums[i];
int right = sum - cur;
if (i == 0 || i == nums.length - 1) {
i++;
continue;
}
while (idx1 <= i && sum1 <= cur - sum1) {
sum1 += nums[idx1++];
}
while (idx2 < idx1 && cur - sum2 > right) {
sum2 += nums[idx2++];
}
if (idx1 > idx2) {
res = (res + idx1 - idx2) % 1000_000_007;
}
i++;
}
return (int) res;
}
}