For this Leetcode question, it seems that if I use the following code, it will pass the online judge:
Given a non-empty array nums containing only positive integers, find if the array can be partitioned into two subsets such that the sum of elements in both subsets is equal.
Example 1:
Input: nums = [1,5,11,5]
Output: true
Explanation: The array can be partitioned as [1, 5, 5] and [11].
Example 2:
Input: nums = [1,2,3,5]
Output: false
Explanation: The array cannot be partitioned into equal sum subsets.
Constraints:
1 <= nums.length <= 200
1 <= nums[i] <= 100
Solution:
class Solution:
def canPartition(self, nums: List[int]) -> bool:
@cache
def dp(i, s):
if s == 0:
return True
if i == 0 or s<0:
return False
if nums[i]<=s:
return dp(i-1, s) or dp(i-1, s-nums[i])
else:
return dp(i-1, s)
total = sum(nums)
if total%2 != 0:
return False
half = total//2
return dp(len(nums)-1, half)
However, if I change the or operator in the dp function to |, the algorithm will run into TLE (Time Limited Exceeded), although the answers are still correct:
class Solution:
def canPartition(self, nums: List[int]) -> bool:
@cache
def dp(i, s):
if s == 0:
return True
if i == 0 or s<0:
return False
if nums[i]<=s:
return dp(i-1, s) | dp(i-1, s-nums[i])
else:
return dp(i-1, s)
total = sum(nums)
if total%2 != 0:
return False
half = total//2
return dp(len(nums)-1, half)
I know | is meant for binary operations. But does this mean that | is slow if applied to boolean values?
