Click here for the google spreadsheet organizing the questions by category and linked to the solution I wrote for each of them. This is always up to date with the README (with the power of a python script and GitHub workflows).
| Number | Question | Hints | Python Solution | C++ Solution |
|---|---|---|---|---|
| 1 | Two Sum | Use a hash table to keep track of the indices of the numbers you've encountered so far. | Python Solution | C++ Solution |
| 24 | Swap Nodes in Pairs | Implement both the iterative and recursive solution. What do we do if the linked list has an odd number of nodes? | Python Solution | |
| 56 | Merge Intervals | Sort the intervals by increasing start time. | Python Solution | |
| 66 | Plus One | Try iterating through each digit backwards. What do you do when the digit is a 9? | Python Solution | |
| 88 | Merge Sorted Array | Look at one element from each of the arrays, compare them, and make a decision depending on their relation to each other. | Python Solution | |
| 122 | Best Time to Buy and Sell Stock II | What should we do every time there is a valley followed by a peak in price? | Python Solution | |
| 206 | Reverse Linked List | Try a recursive solution. Split the list up into the first node and the rest of the list. | Python Solution | |
| 217 | Contains Duplicate | Maintain a hash set that keeps track of the numbers we've encountered so far. | Python Solution | |
| 344 | Reverse String | Use the two pointer approach. Try implementing an iterative and recursive solution. | Python Solution | |
| 392 | Is Subsequence | Use two pointers to iterate through the two strings simultaneously. | Python Solution | |
| 409 | Longest Palindrome | Create a hash table keeping track of the number of occurrences of each character. How many of each can we include in our longest palindrome? | Python Solution | |
| 455 | Assign Cookies | Sort the greed factors and cookies in decreasing (or increasing) order. What can we do with these sorted versions of the inputs? | Python Solution | |
| 763 | Partition Labels | How can be apply a modified version of the merge intervals algorithm to solve this question? | Python Solution | |
| 771 | Jewels and Stones | Python Solution | ||
| 921 | Minimum Add to Make Parentheses Valid | Keep track of the number of open "(" parens as you iterate through the sequence. | Python Solution | |
| 1002 | Find Common Characters | Keep track of the common characters and their occurrences in a hash table. | Python Solution | |
| 1207 | Unique Number of Occurrences | Keep track of the numbers and their number of occurrences in a hash table. | Python Solution | |
| 1338 | Reduce Array Size to The Half | Create a max heap sorted by the number of occurrences of each number | Python Solution | |
| 1338 | How Many Numbers Are Smaller Than the Current Number | Maintain a running sum in an array | Python Solution | |
| 1512 | Number of Good Pairs | Keep track of number of occurrences in a hash table. | Python Solution |