The higher is the bar, the more you're expected to use dynamic programming (DP) during an interview. This technique requires a lot of practice to grasp; if you've mastered the recursion, DP is the next level.
This problem appeared on LeetCode weekly contest #121, and it's a good problem to practice the DP thinking.
Problem Description
In a country popular for train travel, you have planned some train travelling one year in advance. The days of the year that you will travel is given as an array days. Each day is an integer from 1 to 365.
Train tickets are sold in 3 different ways:
- 1-day pass is sold for costs[0] dollars;
- 7-day pass is sold for costs[1] dollars;
- 30-day pass is sold for costs[2] dollars.
The passes allow that many days of consecutive travel. For example, if we get a 7-day pass on day 2, then we can travel for 7 days: day 2, 3, 4, 5, 6, 7, and 8.
Return the minimum number of dollars you need to travel every day in the given list of days.
