河南省第四届程序设计大赛--Substring
2011-08-04 10:06
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描述
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.
Note well: The substring and its reversal may overlap partially or completely. The entire original string is itself a valid substring . The best we can do is
find a one character substring, so we implement the tie-breaker rule of taking the earliest one first.
输入
The first line of input gives a single integer, 1 ≤ N ≤ 10, the number of test cases. Then follow, for each test case, a line containing between 1 and 50
characters, inclusive. Each character of input will be an uppercase letter ('A'-'Z').
输出
Output for each test case the longest substring of input such that the reversal of the substring is also a substring of input
样例输入
3
ABCABA
XYZ
XCVCX
样例输出
ABA
X
XCVCX
很一般的一道题,类似回文字串。但不同的是回文子串的意思是正着看和倒着看是相同的。比如ABCDBA的最长回文字串是A,但这道题的意思是,the reversal of the substring is also a substring of input。就是它的逆子串也存在在这个字符串中,如上例,结果应该是AB。这点很关键,读题一点要仔细,要不然就会想当然。就这么一点错误,可能你再检查N次也不知道哪里错了。
思路很简单:
1.
代码如下:
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.
Note well: The substring and its reversal may overlap partially or completely. The entire original string is itself a valid substring . The best we can do is
find a one character substring, so we implement the tie-breaker rule of taking the earliest one first.
输入
The first line of input gives a single integer, 1 ≤ N ≤ 10, the number of test cases. Then follow, for each test case, a line containing between 1 and 50
characters, inclusive. Each character of input will be an uppercase letter ('A'-'Z').
输出
Output for each test case the longest substring of input such that the reversal of the substring is also a substring of input
样例输入
3
ABCABA
XYZ
XCVCX
样例输出
ABA
X
XCVCX
很一般的一道题,类似回文字串。但不同的是回文子串的意思是正着看和倒着看是相同的。比如ABCDBA的最长回文字串是A,但这道题的意思是,the reversal of the substring is also a substring of input。就是它的逆子串也存在在这个字符串中,如上例,结果应该是AB。这点很关键,读题一点要仔细,要不然就会想当然。就这么一点错误,可能你再检查N次也不知道哪里错了。
思路很简单:
1.
代码如下:
#include<iostream> #include<cstdio> #include<string> #include<algorithm> using namespace std; int main() { int ncase, i, j, maxlen; scanf("%d", &ncase); while(ncase--) { string str, tmp, res; //str原始数据,tmp倒置str,res相同子串 cin>>str; tmp = str; reverse(tmp.begin(), tmp.end()); //倒置 maxlen = 0; for(i = 0; i < str.size(); ++i) { for(j = 1; j <= str.size() - i; ++j) //j代表截取的长度 { if(tmp.find(str.substr(i, j)) != string::npos) //如果截取匹配 { if(j > maxlen) { maxlen = j; //长度更新 res = str.substr(i, j); //最长子串 } } } } cout<<res<<endl; } return 0; }
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