Problems
July 17, 2022
Target sum
We will first solve it with brute force using recursion and then use memoization to make it efficient. For recursion, we can think about the base case, we will start our index at the number of...
ReadJuly 17, 2022
Unique paths
We will first solve it with brute force using recursion and then use memoization to make it efficient. For recursion, we can think about the base case, if our current position is out of bound, then...
ReadJuly 16, 2022
Number of 1 bits
We can have a repeatative pattern if we look at the most significant bit. For example, lets look the following table- Number Binary 0 000 1 001 2 010 3 011 4...
ReadJuly 16, 2022
Course schedule II
This is a classing cycle detect graph problem. We will first convert our edge list to adjacency list. Then we use white-grey-black algorithm to detect cycle. At first every node will be in our white...
ReadJuly 16, 2022
Course schedule
This is a classing cycle detect graph problem. We will first convert our edge list to adjacency list. Then we use white-grey-black algorithm to detect cycle. At first every node will be in our white...
ReadJuly 16, 2022
Missing number
We can XOR the same number to even it out, for example 3^3 or 5^5 will always be 0. That means we can XOR every number form 1 to number of element in our input array and then XOR the input numbers...
ReadJuly 16, 2022
Reverse bits
We can iterate over all 32 bits of our given number, then put it on the opposite bit or our result. If we take i-th bit, we will put it in the (31-i)th bit of our result. Time Complexity: O(1), as...
ReadJuly 16, 2022
Valid parentheses
We can iterate over each characters of the string, and if it's a opening braket, we push it to the stack. If not, then we check, if it matches the top of the stack braket. If matches then we pop it...
ReadJuly 15, 2022
Container with most water
We will take two pointers, one at the beginning and another at the end. Then we calculate the water in between by taking the min value of this 2 position and multiply by the difference of these...
ReadJuly 15, 2022
Merge two sorted list
This approach is very much like merge sort. We took 2 pointers for 2 list, compare thier values, and assign the smaller one to our new list. Then we move that pointer to next node. We go through the...
Read