The key of solving this problem is to use a stack. But before we do that we need to split the string based on /. This way it will give us the parts between slashes which actually determines if we… Read More »Leetcode 71 Simplify Path
The key of solving this problem is to use a stack. Whenever we see an open parenthesis we push it to the stack, when we see an close parenthesis we check if it matches the latest one in the stack,… Read More »Leetcode 20 Valid Parentheses
The key of solving this problem is to sort the array first in ascending order based on the end value of each element because we want to get the overlapping part of each balloon. By sorting it this way, we… Read More »Leetcode 452 Minimum Number of Arrows to Burst Balloons
Initially, the interval we are trying to merge in is newInterval, as we loop through the array, it might change depending on the current interval’s start and end values. We either merge the 2 intervals , OR we move on… Read More »Leetcode 57 Insert Interval
The key to solve this problem is to sort the array first based on the lower bound of each interval. e.g With this sorted array, we loop through the array once and check each interval to see if it can… Read More »Leetcode 56 Merge Intervals
This problem can be solved by using 2 pointers. One represents the left boundary of the interval the other for the right boundary. Then we just need to move the 2 pointers by checking if the next number is consecutive… Read More »Leetcode 228 Summary Ranges
The key for the solution is the sort the nums array first before we loop through it. In each iteration, we need to check a couple of things: Solution
We use a map the keep some information for each number in the array. The key would be the number itself, the value is a map too to keep the upper bound and lower of the index for a valid… Read More »Leetcode 219 Contains Duplicate II
The key for this problem is how to check if two words are anagrams. One good way is to encode the word in a way that anagrams have the same encoding. The way we are encoding is to calculate the… Read More »Leetcode 49 Group Anagrams
The intuition is pretty straight forward which is to use map. But we have to keep two separate maps to record the mapping from s to t and the other from t to s. Then we loop through s and… Read More »Leetcode 205 Isomorphic Strings