Partition Array Into Three Parts With Equal Sum

LintCode Q 1013 - Partition Array Into Three Parts With Equal Sum

Given an array A of integers, return true if and only if we can partition the array into three non-empty parts with equal sums.
Formally, we can partition the array if we can find indexes i+1 < j with (A[0] + A[1] + … + A[i] == A[i+1] + A[i+2] + … + A[j-1] == A[j] + A[j-1] + … + A[A.length - 1])

Example 1:
Input: [0,2,1,-6,6,-7,9,1,2,0,1] ; Output: true
Explanation: 0 + 2 + 1 = -6 + 6 - 7 + 9 + 1 = 2 + 0 + 1

Example 2:
Input: [0,2,1,-6,6,7,9,-1,2,0,1] ; Output: false

Example 3:
Input: [3,3,6,5,-2,2,5,1,-9,4] ; Output: true
Explanation: 3 + 3 = 6 = 5 - 2 + 2 + 5 + 1 - 9 + 4

Note:

• 3 <= A.length <= 50000
• -10000 <= A[i] <= 10000

Solution

Code:

public int partitionDisjoint(int[] A) {
	
	int sum = Arrays.stream(A).sum();

	if (sum % 3 != 0) return false;

	int currSum = 0, count = 0;
	for (int num: A) {
		currSum += num;
		if (currSum == sum / 3) {
			count++;
			currSum = 0;
			if (count == 3) 
				return true;
		}
	}

	return false;
}