linked list - get length - save other information about contents Two pointers - ‘race car’ strategy with one regular pointer, and one fast pointer Dummy node - helpful for preventing errors when returning ‘head’
the problem (hash map, queue, binary search, …) See if there are any speciﬁc techniques that you can apply (ie : using a dummy node, or taking multiple passes)
solve the problem Can you create any ‘magic’ helper methods that would simplify the solution? (ie : getLength(), reverse() ) Talk through different approaches you can take, and their tradeoffs
solve the problem Can you create any ‘magic’ helper methods that would simplify the solution? (ie : getLength(), reverse() ) Talk through different approaches you can take, and their tradeoffs Be able to verbally describe your approach and explain how an example input would produce the desired output
start by understanding the question and running through an example 1->2->3->4->5, n = 2 return 1->2->3->5 Let’s assume we start without any time / space constraints. So our goal is to ﬁgure out ANY kind of solution to produce the right answer
Are there any special techniques that we can use to help make this easier? -> We can take a ﬁrst pass through the linked list to store the elements in an array
Are there any special techniques that we can use to help make this easier? -> We can take a ﬁrst pass through the linked list to store the elements in an array -> We can also take a pass to get the length of the linked list
Are there any special techniques that we can use to help make this easier? -> We can take a ﬁrst pass through the linked list to store the elements in an array -> We can also take a pass to get the length of the linked list Plan : What are some different ways we can solve this problem?
Are there any special techniques that we can use to help make this easier? -> We can take a ﬁrst pass through the linked list to store the elements in an array -> We can also take a pass to get the length of the linked list Plan : What are some different ways we can solve this problem? 1) We can store the elements in an array, get the length of the array, and then rebuild our list excluding the nth to last node
Are there any special techniques that we can use to help make this easier? -> We can take a ﬁrst pass through the linked list to store the elements in an array -> We can also take a pass to get the length of the linked list Plan : What are some different ways we can solve this problem? 1) We can store the elements in an array, get the length of the array, and then rebuild our list excluding the nth to last node 2) We can follow the ﬁrst idea, but instead of storing things in an array, remove the reference to the nth to last node the second time we iterate through the list
Are there any special techniques that we can use to help make this easier? -> We can take a ﬁrst pass through the linked list to store the elements in an array -> We can also take a pass to get the length of the linked list Plan : What are some different ways we can solve this problem? 1) We can store the elements in an array, get the length of the array, and then rebuild our list excluding the nth to last node 2) We can follow the ﬁrst idea, but instead of storing things in an array, remove the reference to the nth to last node the second time we iterate through the list What would be the space / time complexity of our solution?
1) make initial pass through linked list to get length 2) make second pass to remove any reference to nth to last node Let’s draw out how this might work with an example Given linked list 1->2->3, n = 1 (we want to return 1->2)
1) make initial pass through linked list to get length 2) make second pass to remove any reference to nth to last node Let’s draw out how this might work with an example Given linked list 1->2->3, n = 1 (we want to return 1->2) First pass, we get length = 3. Since n = 1, that means we want to remove the 3 -1 = 2 node (with index starting at 0)
1) make initial pass through linked list to get length 2) make second pass to remove any reference to nth to last node Let’s draw out how this might work with an example Given linked list 1->2->3, n = 1 (we want to return 1->2) First pass, we get length = 3. Since n = 1, that means we want to remove the 3 -1 = 2 node (with index starting at 0) As we iterate through the list.. at node 1 -> numberOfNodesSeen = 0
1) make initial pass through linked list to get length 2) make second pass to remove any reference to nth to last node Let’s draw out how this might work with an example Given linked list 1->2->3, n = 1 (we want to return 1->2) First pass, we get length = 3. Since n = 1, that means we want to remove the 3 -1 = 2 node (with index starting at 0) As we iterate through the list.. at node 1 -> numberOfNodesSeen = 0 at node 2-> numberOfNodesSeen = 1
1) make initial pass through linked list to get length 2) make second pass to remove any reference to nth to last node Let’s draw out how this might work with an example Given linked list 1->2->3, n = 1 (we want to return 1->2) First pass, we get length = 3. Since n = 1, that means we want to remove the 3 -1 = 2 node (with index starting at 0) As we iterate through the list.. at node 1 -> numberOfNodesSeen = 0 at node 2-> numberOfNodesSeen = 1 at node 3 -> numberOfNodesSeen = 2 -> at this point we need to set node 2’s next to be node 3’s next!
1) make initial pass through linked list to get length 2) make second pass to remove any reference to nth to last node Let’s draw out how this might work with an example Given linked list 1->2->3, n = 1 (we want to return 1->2) First pass, we get length = 3. Since n = 1, that means we want to remove the 3 -1 = 2 node (with index starting at 0) As we iterate through the list.. at node 1 -> numberOfNodesSeen = 0, previousNode = null at node 2-> numberOfNodesSeen = 1, previousNode = 1 at node 3 -> numberOfNodesSeen = 2, previousNode = 2 -> we set previousNode.next = node.next (node 3’s next = null)
Planning the solution to the problem Verbally discuss 2-3 ways to solve the problem and discuss tradeoffs with each approach Think about whether there are any 'magical' helper methods that would greatly help you solve the problem
Planning the solution to the problem Verbally discuss 2-3 ways to solve the problem and discuss tradeoffs with each approach Think about whether there are any 'magical' helper methods that would greatly help you solve the problem Walk through 2 example inputs and explain how the solution would produce the desired output