Find the smallest element greater than current element
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my question is that given a list of integers (lets say A), for each element A[i], find the smallest element A[j] which could satisfy A[i] < A[j] and i < j. Return -1 if there is no such element.
For example, given [4,2,1,9,3], return [9,3,3,-1,-1]
I have come up with a brute force solution which costs $O(n^2)$, but I'm wondering if there could be a more efficient solution.
algorithms arrays
edited 36 mins ago
xskxzr
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asked 5 hours ago
Austin
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up vote
3
down vote
favorite
my question is that given a list of integers (lets say A), for each element A[i], find the smallest element A[j] which could satisfy A[i] < A[j] and i < j. Return -1 if there is no such element.
For example, given [4,2,1,9,3], return [9,3,3,-1,-1]
I have come up with a brute force solution which costs $O(n^2)$, but I'm wondering if there could be a more efficient solution.
algorithms arrays
edited 36 mins ago
xskxzr
3,3871730
asked 5 hours ago
Austin
161
New contributor
Austin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
How difficult would this problem be if you had an array of integers, sorted in ascending order?
– gnasher729
5 hours ago
I believe that this could be done in as little as O(n)! I'll elaborate when I have access to a computer.
– xuq01
3 hours ago
I think my solution is wrong; the minimum time complexity must be O(n log n) I think.
– xuq01
6 mins ago
add a comment |
up vote
3
down vote
favorite
up vote
3
down vote
favorite
my question is that given a list of integers (lets say A), for each element A[i], find the smallest element A[j] which could satisfy A[i] < A[j] and i < j. Return -1 if there is no such element.
For example, given [4,2,1,9,3], return [9,3,3,-1,-1]
I have come up with a brute force solution which costs $O(n^2)$, but I'm wondering if there could be a more efficient solution.
algorithms arrays
edited 36 mins ago
xskxzr
3,3871730
asked 5 hours ago
Austin
161
New contributor
Austin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
my question is that given a list of integers (lets say A), for each element A[i], find the smallest element A[j] which could satisfy A[i] < A[j] and i < j. Return -1 if there is no such element.
For example, given [4,2,1,9,3], return [9,3,3,-1,-1]
I have come up with a brute force solution which costs $O(n^2)$, but I'm wondering if there could be a more efficient solution.
algorithms arrays
algorithms arrays
edited 36 mins ago
xskxzr
3,3871730
asked 5 hours ago
Austin
161
New contributor
Austin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 36 mins ago
xskxzr
3,3871730
asked 5 hours ago
Austin
161
New contributor
Austin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 36 mins ago
xskxzr
3,3871730
edited 36 mins ago
xskxzr
3,3871730
edited 36 mins ago
xskxzr
3,3871730
3,3871730
asked 5 hours ago
Austin
161
New contributor
Austin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 5 hours ago
Austin
161
asked 5 hours ago
Austin
161
161
New contributor
Austin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Austin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Austin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
How difficult would this problem be if you had an array of integers, sorted in ascending order?
– gnasher729
5 hours ago
I believe that this could be done in as little as O(n)! I'll elaborate when I have access to a computer.
– xuq01
3 hours ago
I think my solution is wrong; the minimum time complexity must be O(n log n) I think.
– xuq01
6 mins ago
add a comment |
How difficult would this problem be if you had an array of integers, sorted in ascending order?
– gnasher729
5 hours ago
I believe that this could be done in as little as O(n)! I'll elaborate when I have access to a computer.
– xuq01
3 hours ago
I think my solution is wrong; the minimum time complexity must be O(n log n) I think.
– xuq01
6 mins ago
How difficult would this problem be if you had an array of integers, sorted in ascending order?
– gnasher729
5 hours ago
How difficult would this problem be if you had an array of integers, sorted in ascending order?
– gnasher729
5 hours ago
I believe that this could be done in as little as O(n)! I'll elaborate when I have access to a computer.
– xuq01
3 hours ago
I believe that this could be done in as little as O(n)! I'll elaborate when I have access to a computer.
– xuq01
3 hours ago
I think my solution is wrong; the minimum time complexity must be O(n log n) I think.
– xuq01
6 mins ago
I think my solution is wrong; the minimum time complexity must be O(n log n) I think.
– xuq01
6 mins ago
add a comment |
1 Answer
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up vote
2
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A better solution would be using a balanced binary search tree.
You can process the elements from the right to left and for each element you find the vertex in the tree with the smallest key greater than this element (a search query on the tree suffice) and then you add the element to the tree.
Total complexity is $O(nlog(n))$ since we are iterating over the elements once and having one query and one insert operations in each iteration.
answered 5 hours ago
narek Bojikian
3316
add a comment |
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1 Answer
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active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
2
down vote
A better solution would be using a balanced binary search tree.
You can process the elements from the right to left and for each element you find the vertex in the tree with the smallest key greater than this element (a search query on the tree suffice) and then you add the element to the tree.
Total complexity is $O(nlog(n))$ since we are iterating over the elements once and having one query and one insert operations in each iteration.
answered 5 hours ago
narek Bojikian
3316
add a comment |
up vote
2
down vote
A better solution would be using a balanced binary search tree.
You can process the elements from the right to left and for each element you find the vertex in the tree with the smallest key greater than this element (a search query on the tree suffice) and then you add the element to the tree.
Total complexity is $O(nlog(n))$ since we are iterating over the elements once and having one query and one insert operations in each iteration.
answered 5 hours ago
narek Bojikian
3316
add a comment |
up vote
2
down vote
up vote
2
down vote
A better solution would be using a balanced binary search tree.
You can process the elements from the right to left and for each element you find the vertex in the tree with the smallest key greater than this element (a search query on the tree suffice) and then you add the element to the tree.
Total complexity is $O(nlog(n))$ since we are iterating over the elements once and having one query and one insert operations in each iteration.
answered 5 hours ago
narek Bojikian
3316
A better solution would be using a balanced binary search tree.
You can process the elements from the right to left and for each element you find the vertex in the tree with the smallest key greater than this element (a search query on the tree suffice) and then you add the element to the tree.
Total complexity is $O(nlog(n))$ since we are iterating over the elements once and having one query and one insert operations in each iteration.
answered 5 hours ago
narek Bojikian
3316
edited 4 hours ago
answered 5 hours ago
narek Bojikian
3316
answered 5 hours ago
narek Bojikian
3316
answered 5 hours ago
narek Bojikian
3316
3316
add a comment |
add a comment |
Austin is a new contributor. Be nice, and check out our Code of Conduct.
Austin is a new contributor. Be nice, and check out our Code of Conduct.
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How difficult would this problem be if you had an array of integers, sorted in ascending order?
– gnasher729
5 hours ago
I believe that this could be done in as little as O(n)! I'll elaborate when I have access to a computer.
– xuq01
3 hours ago
I think my solution is wrong; the minimum time complexity must be O(n log n) I think.
– xuq01
6 mins ago