We have an array A
of non-negative integers.
For every (contiguous) subarray B = [A[i], A[i+1], ..., A[j]]
(with i <= j
), we take the bitwise OR of all the elements in B
, obtaining a result A[i] | A[i+1] | ... | A[j]
.
Return the number of possible results. (Results that occur more than once are only counted once in the final answer.)
Example 1:
Input: [0] Output: 1 Explanation: There is only one possible result: 0.
Example 2:
Input: [1,1,2] Output: 3 Explanation: The possible subarrays are [1], [1], [2], [1, 1], [1, 2], [1, 1, 2]. These yield the results 1, 1, 2, 1, 3, 3. There are 3 unique values, so the answer is 3.
Example 3:
Input: [1,2,4] Output: 6 Explanation: The possible results are 1, 2, 3, 4, 6, and 7.
Note:
1 <= A.length <= 50000
0 <= A[i] <= 10^9
我们有一个非负整数数组 A。对于每个(连续的)子数组 B = [A[i], A[i+1], ..., A[j]] ( i <= j),我们对 B 中的每个元素进行按位或操作,获得结果 A[i] | A[i+1] | ... | A[j]。返回可能结果的数量。(多次出现的结果在最终答案中仅计算一次。)
- 给出一个数组,要求求出这个数组所有的子数组中,每个集合内所有数字取
|
运算以后,不同结果的种类数。 - 这道题可以这样考虑,第一步,先考虑所有的子数组如何得到,以
[001, 011, 100, 110, 101]
为例,所有的子数组集合如下:
[001] [001011] [011] [001011100] [011100] [100] [001011100110] [011100110] [100110] [110] [001011100110101] [011100110101] [100110101] [110101] [101]
可以发现,从左往右遍历原数组,每次新来的一个元素,依次加入到之前已经生成过的集合中,再以自己为单独集合。这样就可以生成原数组的所有子集。
- 第二步,将每一行的子集内的所有元素都进行
|
运算,得到:
001011011111111100111111110110111111111111101
- 第三步,去重:
001011111100111110111101
由于二进制位不超过 32 位,所以这里每一行最多不会超过 32 个数。所以最终时间复杂度不会超过 O(32 N),即 O(K * N)。最后将这每一行的数字都放入最终的 map 中去重即可。