Non-Adjacent Combination Sum - Amazon Top Interview Questions
Problem Statement :
You are given a list of positive integers nums and an integer k. Return whether there exists a combination of integers in nums such that their sum is k and none of those elements are adjacent in the original list. Constraints n * k ≤ 100,000 where n is the length of nums Example 1 Input nums = [1, 2, 2, 3] k = 4 Output True Explanation We can pick [1, 3] since they are non-adjacent and sums to 4 Example 2 Input nums = [1, 3, 1] k = 4 Output False Explanation We can't pick [1, 3] or [3, 1] since they are adjacent.
Solution :
Solution in C++ :
bool solve(vector<int>& nums, int k) {
if (k == 0) return true;
bitset<100005> has, nohas;
nohas.set(0);
for (int num : nums) {
bitset<100005> nhas, nnohas;
nhas = (nohas << num);
if (nhas[k]) return true;
nnohas = (has | nohas);
has = nhas;
nohas = nnohas;
}
return false;
}
Solution in Python :
class Solution:
def solve(self, nums, k):
@lru_cache(None)
def f(total, idx):
if total > k:
return False
if total == k:
return True
if idx >= len(nums):
return False
return f(total + nums[idx], idx + 2) or f(total, idx + 1)
return f(0, 0)
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