Blind 75 **Approach** **Big O Analysis** Leave a like if this helped! If you have any questions/issues with the code, let me know in the comments! 121. Best Time to Buy and Sell Stock Approach In terms of approach, we want to find the maximum profit possible and the way we're going to do that as we can keep track of the minimum value we’ve encountered thus far. By comparing the profit of “selling”(current value - current minimum value) to the max profit, we can continually update the max profit. Then, at the end of the iteration we get the final Max profit possible. Code break down MinValue is equal to 10^5 because that is greater than any value you can encounter in the list. Max profit is set to 0 because that ensures that if nothing changes the max profit, it'll yield 0. Now we can continually update the min value if a lower price is encountered and update the max profit if a greater profit is encountered. Big O break down So this is clearly O(n) time because we are iterating through the list one time and every iteration has constant time calculations. 217. Contains Duplicate Approach so sure we can check if the length of the list numbs is equal to the length of a set of the list nums. However this is probably not how this is meant to be salt. Instead, we can keep track of previous values that have been encountered with a set, and every time we encounter a new element check if it is found within that set. Big'o break down This is Big O of n because adding to a set end checking if a value is in a set is constant time. in the worst case alliterate through the entire array. 152. Maximum Product Subarray Approach So, the first thing that comes to mind is using the same approach as the maximum sum subarray, however, this breaks down with multiplying negative numbers because a negative number can lead you to a maximum later down the line. This means we must keep track of both the current maximum product and the current minimum product. As we iterate through the list, we find the current minimum by seeing if the current element is smaller than either the previous maximum*the current element or the previous minimum *current element because both of them could lead to minimums. We do the same for the current maximum because multiplication could lead to both maximums or minimums. Then, we can update the total maximum by seeing if the current maximum is the greatest we have encountered thus far. Big O Break Down This is Big O N because we are iterating through the list one time and every iteration has constant time calculations. 322. Coin Change Approach Must start on a single coin and for each recursive call try to find the min number of coins to make amount - current coin by looping through all the numbers. Then return this number. Can use memoization to improve the speed and memory. Keep track of the min number of coins for the current amount, can remove branches in the overall recursive stack to improve speed and memory. Big O break down With memoization the runtime is O(n*m). Others 108. Convert Sorted Array to Binary Search Tree Hello Saudi Arabia is already sorted which means to start populating the tree the binary search tree we have to find the root note and once we find the node then we could set the value to the current value and then at the left note then we can add the right note but in order to add love note we need to know what the weather is equal to. What does equal to the root of that of its own tree which because it's a binary search tree must be in the middle of all the values of that subarray. this means we have to find multiple subarrays and then Subways in those subarrays to calculate the middle notes in each of them. This is a recursive pattern. So the easiest way to solve this is a recursive function that calculates the middle which is the route and then calls the recursive function again to find the value of the left node using a separate subarray then calling the crucifixion to find the value of the right note using a separate Subway and finally once we've got those returning the route so the value is set in those notes once it back propagates the recursive function. new one Big O break down new one Dysfunction this solution is Big O time a van. this is because every value in the list must be visited which is and different values.
