# 【急！！】求高手关于Huffman Codes的一道程序题

In 1953, David A. Huffman published his paper “A Method for the Construction of Minimum-Redundancy Codes”, and hence printed his name in the history of computer science. As a professor who gives the final exam problem on Huffman codes, I am encountering a big problem: the Huffman codes are NOT unique. For example, given a string “aaaxuaxz”, we can observe that the frequencies of the characters 'a', 'x', 'u' and 'z' are 4, 2, 1 and 1, respectively. We may either encode the symbols as {'a'=0, 'x'=10, 'u'=110, 'z'=111}, or in another way as {'a'=1, 'x'=01, 'u'=001, 'z'=000}, both compress the string into 14 bits. Another set of code can be given as {'a'=0, 'x'=11, 'u'=100, 'z'=101}, but {'a'=0, 'x'=01, 'u'=011, 'z'=001} is NOT correct since “aaaxuaxz” and “aazuaxax” can both be decoded from the code 00001011001001. The students are submitting all kinds of codes, and I need a computer program to help me determine which ones are correct and which ones are not.

Input Specification:
Your program must read test cases from a file “input.txt”. The input file consists of several test cases. For each test case, the first line gives an integer N (63), then followed by a line that contains all the N distinct characters and their frequencies in the following format:
c f c f ... c[N] f[N]
where c[i] is a character chosen from {'0' - '9', 'a' - 'z', 'A' - 'Z', '_'}, and f[i] is the frequency of c[i] and is an integer no more than 1000. The next line gives an integer M (1000), then followed by M student submissions. Each student submission consists of N lines, each in the format:
c[i] code[i]
where c[i] is the i-th character and code[i] is a string of '0's and '1's.
The input ends with N being 0, and that case must NOT be processed.

Output Specification:
For each test case, output to a file “output.txt”. First print in a line "Case #:" where # is the case number starting from 1. Then in the following M lines, either print “Yes” if the student’s submission is correct, or “No” if not.

Sample Input:
4
a 4 x 2 u 1 z 1
2
a 0
x 10
u 110
z 111
a 0
x 01
u 011
z 001
7
A 1 B 1 C 1 D 3 E 3 F 6 G 6
2
A 00000
B 00001
C 0001
D 001
E 01
F 10
G 11
A 000
B 001
C 010
D 011
E 100
F 101
G 110
0
Sample Output:
Case 1:
Yes
No
Case 2:
Yes
No

...全文
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12 条回复

sleepwater 2008-12-11
[Quote=引用 1 楼 iamtheteacher 的回复:]

CYLL
[/Quote]

CYLL 我错了，本想求个算法而已。

iamtheteacher 2008-12-09

CYLL

3.2w+