Hashing Study Guide

CS61B

B LEVEL

2.

A LEVEL

这道题跟Lecture 23的slide上一个food for thoughts是一样的：

我认为是因为如果M是31的倍数，那么hashCode最后取模都相当于最后一个Sn-1取模，这里的话就是String的最后一个字母相等的话，这些items都要挤到一个bucket里，就会发生collision,这不是好的hashCode.

参考：
Why use a prime number in hashCode?
[Why does Java's hashCode() in String use 31 as a multiplier?](Why does Java's hashCode() in String use 31 as a multiplier?)

1.

跟上面那道题类似，来自Algorithm 4th edition的说法（base-10 numbers就是十进制数）：

2.

3.Find 2 strings in Java that hash to the same value (writing code is probably best).
FB 2236
Ea 2236

4.CS61B Fall 2009 midterm, #4 (really beautiful problem)

后面题目不想做了，看不大懂。