LeetCode_1013.将数组分成和相等的三个部分
给你一个整数数组 A
,只有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:
输入:[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
提示:
3 <= A.length <= 50000
-10^4 <= A[i] <= 10^4
C#代码
public class Solution {
public bool CanThreePartsEqualSum(int[] A) {
if (A.Length < 3) return false;
int sum = 0;
int len = A.Length;
for (int i = 0; i < len; i++) sum += A[i];
if (sum % 3 != 0) return false;
int mid = sum / 3;
int sum1 = 0, sum2 = 0;
int left = 0, right = len - 1;
do
{
sum1 += A[left];
} while (sum1 != mid && left++ < right);
if (sum1 != mid) return false;
do
{
sum2 += A[right];
} while (sum2 != mid && right-- > left);
if (sum2 != mid) return false;
if (right - left <= 1) return false;
return true;
}
}