请英语高手帮我找一下动词变化规律

我的老师在给我们上动词过去式的时候给我们讲了几个规律，有一个规律我给忘了，请各位高手帮我说一下他的规律;
原形 过去式
find found
think thought
bring brought
fight fought
buy bought
teach taught
请高手帮帮忙，看一下这几个不规则动词变化有什么规律，我们老师说有一小点，但我忘了，还请各位帮帮忙，说一下。

不规则动词分类表
1. A---A---A型（现在式、过去式和过去分词同形）
动词原形（现在式） 过去式 过去分词
cost cost cost 花费
cut cut cut 割，切
hit hit hit 打
let let let 让
put put put 放下
read read read 读
hurt hurt hurt 伤
2. A---A---B型（现在式和过去式同形）
beat beat beaten 打
3. A---B---A型（现在式和过去分词同形）
come came come 来
become became become 变
run ran run 跑
4. A ---B ---B型
（1）在动词原形后加一个辅音字母d或t构成过去式或过去分词。
burn burnt burnt 燃烧
learn learned/learnt learned/learnt 学习
mean meant meant 意思
hear heard heard 听见
（2）把动词原形的最后一个辅音字母“d”改为“t” 构成过去式或过去分词。
build built built 建筑
lend lent lent 借给
lose lost lost 失去
send sent sent 送
spend spent spent 花费

（3）其他
pay paid paid 付
lay laid laid 下蛋
say said said 说

bring brought brought 带来
buy bought bought 买
think thought thought 想

sleep slept slept 睡
keep kept kept 保持
sweep swept swept 扫