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
We use a map the keep records of all the numbers during the process. If at any time the converted number equals to 1 we return true directly, otherwise if the number appeared earlier we return false instead. Solution
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
The idea is pretty simple, we use a map to record the number appearance for each letter from the ransomNote. Then we go to magazine and see if each letter can be used in the ransomNote. Each time we see… Read More »Leetcode 383 Ransom Note
This is an interesting problem which looks complex but essentially there are just 2 steps we need to do this. Solution Javascript: Time Complexity:O(n^2) since we visited all the cells in the matrix Space Complexity:O(1) since it’s in place
This is indeed a very interesting problem. If we simulate the process, there are a couple of key points to notice: Solution Javascript: Time Complexity:O(m*n) since we visited all the cells in the matrix Space Complexity:O(1)
The first thing comes into mind is sliding window since this is a substring related problem. The idea is pretty simple actually. javascript: Time Complexity:We looped through both t and s once, so the time complexity is O(m + n)… Read More »Leetcode 76 Minimum Window Substring
Problem Statement Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules: Note: Examples Constraints Solution Python: Java:
Problem Statement Given an array of integers nums and an integer target, return the indices of the two numbers such that they add up to target. You may assume that each input would have exactly one solution, and you may not use the same… Read More »Leetcode 1 Two Sum