Leetcode(2)_num1020_canThreePartsEqualSum

Leetcode129周赛,将数组分成和相等的三个部分

"""
给定一个整数数组 A，只有我们可以将其划分为三个和相等的非空部分时才返回 true，否则返回 false。

形式上，如果我们可以找出索引 i+1 < j 且满足 (A[0] + A[1] + ... + A[i] == A[i+1] + A[i+2] + ... + A[j-1] == A[j] + A[j-1] + ... + A[A.length - 1]) 就可以将数组三等分。



示例 1：
输出：[0,2,1,-6,6,-7,9,1,2,0,1]
输出：true
解释：0 + 2 + 1 = -6 + 6 - 7 + 9 + 1 = 2 + 0 + 1

示例 2：
输入：[0,2,1,-6,6,7,9,-1,2,0,1]
输出：false


示例 3：
输入：[3,3,6,5,-2,2,5,1,-9,4]
输出：true
解释：3 + 3 = 6 = 5 - 2 + 2 + 5 + 1 - 9 + 4
"""


def canThreePartsEqualSum(A):
    

    a = sum(A)
    index1 = 0
    index2 = 0
    if a % 3 != 0:
        return False
    sum1 = 0
    sum2=0
    for i in range(0, len(A)):
        sum1 += A[i]
        if sum1 == a / 3:
            index1 = i
            break

    for i in range(len(A) - 1, -1, -1):
        sum2 += A[i]
        if sum2 == a / 3:
            index2 = i
            break

    if index1 + 1 < index2:
        return True

    return False


def main():
    A = [0,2,1,-6,6,-7,9,1,2,0,1]
    flag = canThreePartsEqualSum(A)
    print(flag)


if __name__ == '__main__':
    main()