Codeforces Round #253 (Div. 2) B - Kolya and Tandem Repeat

本题要考虑字符串本身就存在tandem，

如测试用例

aaaaaaaaabbb

3

输出结果应该是8而不是6，因为字符串本身的tanderm时最长的

故要考虑字符串本身的最大的tanderm和添加k个字符后最大的tanderm

#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <set>

using namespace std;

int maxTandem(string& str){
    for(int inteval = str.length()/; inteval>=; --inteval){
        for(int i =  ; i <=str.length()-*inteval; ++i){
            bool flag = false;
            for(int j = i,k=i+inteval; j < i+inteval; j++,k++){
                if(str[j] != str[k]){
                    flag = true;
                    break;
                }
            }
            if(!flag) return inteval;
        }
    }
    return ;
}

int main(){
    string str;
    int k;
    cin  >> str >> k;
    int len = str.length();
    if(k>=len){
        cout<<((k+len)% ? k+len-:k+len)<<endl;
    }else{
        int newlen = len+k, startIndex=newlen-newlen/*, p =newlen/;
        for( p = newlen/; p> k;  -- p){
            int startIndex=newlen-p*;
            bool flag = false;
            for(int i = startIndex, j = startIndex+p;  i < min(len,startIndex+p) && j < len; ++ i, ++ j){
                if(str[i] != str[j]){
                    flag = true;
                    break;
                }
            }
            if(!flag) break;
        }
        cout<<*max(p,maxTandem(str))<<endl;
    }
}

本题将上面两个部分合并，即在字符串s后面添加k个‘?’,再对整个字符串搜索

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

using namespace std;

int main(){
    string s;
    int k;
    cin >> s >> k;
    int slen = s.length();
    s+=string(k,'?');
    int len = s.length()/, interval = len;
    for(interval = len; interval >=; interval--){
        bool flag = false;
        for(int p = ; p<= s.length()-*interval; ++ p){
            flag = false;
            for(int i = p, j = p+interval; i < min(slen,p+interval) && j < slen; ++ i, ++ j){
                if(s[j]!= '?' && s[i]!=s[j] ){ flag = true;break;}
            }
            if(!flag) break;
        }
        if(!flag) break;
    }
    cout<<*interval<<endl;
}