动态规划：状态定义才是那道坎
「看得懂题解、自己想不出来」，卡的几乎都是这一步。
Copy the prompt, then pick a model. It plays the interviewer and asks you through it scene by scene instead of handing you the answer.
On a phone with the app installed, the system opens the app directly. Links cannot open external apps inside WeChat — open it in a browser first.
The copied text ends with the answer key the model grades you against. Don't read it yourself first — working it out on your own is the point.
大家练的是转移方程，但转移是状态的推论：状态定对了转移基本自动，状态定错了怎么凑都凑不出来。所以这一份从头到尾只问状态，一个转移方程都不给你。
有一问是照妖镜：你说「dp[i] 表示前 i 个的最优解」，那么 —— 它必须包含第 i 个吗？两种读法对应完全不同的转移和答案位置，而一多半人从没分清过。
第三幕用环形数组把你的状态打穿，然后逼你说出什么叫「合法的状态」。
What this one drills
This prompt in the repo (the answer key is at the end of that file — you'll see it)
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Notes from people who did this one
How to use this
This set teaches rather than interrogates: it guides you instead of pressing until you have nothing left to say. When you're stuck it first asks which layer you're stuck at (never heard of it / know it but not why / know why but can't write it), then decides what to give. Only after guiding you twice on the same point will it spell the answer out — and then it asks you to say it back in your own words.
How to start
- Pick one, open it, copy the prompt.
- Paste it into a brand-new conversation, say nothing, and wait for its first question.
- Trace by hand before you write code — it will interrupt you. Walking through an array of length 2 beats writing the template ten times.
Four commands you can call out at any time
跳过move to the next scene now换个说法explain this bit again from another angle直说吧spell the answer out, then make me say it back复盘jump to the wrap-up and print the review card
Three traps
- Don't read the answer key at the end first — that "how people get it wrong" section is the answer to every question it will ask you.
- Don't rush to code. With algorithms, writing code is the easiest way to hide the fact that you haven't actually thought it through.
- When it starts praising you, point it back to the "don't praise me" rule. Guiding is not coddling.
Can't come up with a solution? Start with defining the DP state. Always off by one? Binary search and prefix sums. Can't recognise the shape of a problem? Monotonic stack and sliding window. The complexity one underpins several others — do it early.
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