Скачать или смотреть Day 321: Minimum Cost For Tickets | DP Explained Step-by-Step (1, 7, 30 Days Trick)

Day 321 of my #300DaysOfCode!
Today I solved LeetCode 983 — Minimum Cost For Tickets, one of the most practical and elegant DP problems.

We want to find the minimum cost to travel on a given set of days using 3 types of passes:

1-day pass

7-day pass

30-day pass

This becomes a dynamic programming problem where dp[i] represents the minimum cost to travel up to day i.

In this video, I explain:

Why we convert days to a set for O(1) lookups

What dp[i] means and how it’s updated

Why days not in the travel list simply inherit dp[i-1]

How the transitions use:

dp[i-1] + cost_of_1_day

dp[i-7] + cost_of_7_day

dp[i-30] + cost_of_30_day

A clean trick using max(0, i-x) to avoid index issues

Full dry run with examples

Final clean implementation

Mastering this helps with interval DP, timeline DP, and “cost minimization” DP patterns.

📌 Full code included
📌 Easy explanation for beginners
📌 Perfect for interviews + DP preparation

👉 Comment which DP problem I should do for Day 322!
👉 Subscribe to support the journey ❤️

#365daysofcode #leetcode #dynamicprogramming #tickets #mincost #dp #codingjourney #python #beginnerprogrammer