1013.py

'''
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
'''

class Solution(object):
    def canThreePartsEqualSum(self, A):
        """
        :type A: List[int]
        :rtype: bool
        """
        total_sum = 0
        for val in A:
            total_sum += val
            
        if(total_sum%3 != 0):
            return False
        
        curr_sum, groups = 0, 0
        for val in A:
            curr_sum += val
            if curr_sum == total_sum/3:
                curr_sum = 0
                groups +=1
        print groups
        return groups == 3