对中国编程资格赛一题的解答
刚才看到一位朋友对中国编程资格赛中一个题目的解答,觉得答案略为复杂了一些。以下是我的解答,请大家指点:
原题:
Problem Statement
You are given a string input. You are to find the longest substring of input such that the reversal of the substring is also a substring of input. In case of a tie, return the string
that occurs earliest in input.
Definition
Class:
ReverseSubstring
Method:
findReversed
Parameters:
string
Returns:
string
Method signature:
string findReversed(string input)
(be sure your method is public)
Notes
-
The substring and its reversal may overlap partially or completely.
-
The entire original string is itself a valid substring (see example 4).
Constraints
-
input will contain between 1 and 50 characters, inclusive.
-
Each character of input will be an uppercase letter ('A'-'Z').
Examples
0)
"XBCDEFYWFEDCBZ"
Returns: "BCDEF"
We see that the reverse of BCDEF is FEDCB, which appears later in the string.
1)
"XYZ"
Returns: "X"
The best we can do is find a one character substring, so we implement the tie-breaker rule of taking the earliest one first.
2)
"ABCABA"
Returns: "ABA"
The string ABA is a palindrome (it's its own reversal), so it meets the criteria.
3)
"FDASJKUREKJFDFASIREYUFDHSAJYIREWQ"
Returns: "FDF"
4)
"ABCDCBA"
Returns: "ABCDCBA"
Here, the entire string is its own reversal.
解答:
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