Leetcode 15. 3Sum

As we have already solved “Two Sum” problem already, let’s reuse our existing knowledge to solve this problem. We know the target and we want to search 3 numbers. We know how to search 2 numbers, so if we fix one number at a time and look for the other two numbers using our previous solution that would solve this problem as well.

Prefer video over text? Watch the explanation here: https://youtu.be/MmhfOzYMYPkMore Leetcode 15. 3Sum

Leetcode 70. Climbing Stairs

Now that we know 3rd step can be reached directly from 1st and 2nd, what will be the number of ways in which we can reach the step 3? It would be all the ways in which we can reach the step 1 (because we can always take 2 steps from here to reach the step 3) + the number of ways in which we can reach the step 2 (because we can always take 1 more step to reach the step 3). … More Leetcode 70. Climbing Stairs

Leetcode #1529: Bulb Switcher IV

Certainly, a “Flip” is a must when the current status of a bulb at index i and it’s the target status are not the same.

Initially all bulbs are OFF i.e. 0 and when a bulb at index i is flipped, every bulb after (in the right -> direction) that bulb gets flipped. So it only makes sense to start getting the status of the bulbs correct int the left to right order. … More Leetcode #1529: Bulb Switcher IV

Leetcode #1503: Last Moment Before All Ants Fall Out of a Plank

The problem is a lot about observation. Observing and analyzing the ant behavior will reveal that the problem is way too tricky to understand but way too easy to implement. The idea is to think of the bigger picture and focus only on the paths of the ants. At any collision, think of it as ants transferring their responsibility … … More Leetcode #1503: Last Moment Before All Ants Fall Out of a Plank

Leetcode #1488: Avoid Flood in The City

When drying lake #L, it is only useful to dry it if it is FULL already. Otherwise, it’s just a waste to dry an empty lake. (Explained this in the code with a small example as well). In short, drying a lake #L only makes sense if it is already FULL and it is going to rain on that lake in future.

Which lake to dry on a day when there is no rain, can not be determined without knowing the rain sequence that is coming next. … More Leetcode #1488: Avoid Flood in The City

Leetcode #1465: Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts

So the only task for us is to find what would be the height and width of each piece after all cuts and then find the piece with maximum height and width. Each cut in the cake, divides the cake into pieces with certain height and certain width. We want to maximize the area … … More Leetcode #1465: Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts