HDU 4731 Minimum palindrome 打表找规律

http://acm.hdu.edu.cn/showproblem.php?pid=4731

就做了两道...也就这题还能发博客了...虽然也是水题

先暴力DFS打表找规律...发现4个一组循环节...尾部特殊判断....然后构造一下...

#include <cstdio>
#include <string>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int ss;
int f(const string& strs) {
    string s("##");
    for(string::const_iterator it = strs.begin(); it != strs.end(); ++it) {
        s.push_back(*it);
        s.push_back('#');
    }
    int len = s.length(), id = 0, mx = 0;
    vector<int> p(len, 0);
    for(int i = 1; i < len; ++i) {
        p[i] = mx > i ? min(mx - i, p[2*id-i]) : 1;
        while(s[i+p[i]] == s[i-p[i]]) {
            ++p[i];
        }
        if(i + p[i] > mx) {
            mx = i + p[i];
            id = i;
        }
    }
    int start = 0, sublen = 0;
    for(int i = 1; i < len; ++i) {
        if(p[i] > sublen) {
            sublen = p[i];
            start = i;
        }
    }
    return sublen - 1;
}
int main(){
    //pre();
    int n,m;
    int T;
    cin>>T;
    for(int t = 1 ; t <= T ; t++){
        scanf("%d%d",&m,&n);
        printf("Case #%d: ",t);
        if(m == 1){
            for(int i = 0 ; i < n ; i++) printf("a");
        }
        else if(m >= 3){
            for(int i = 0 ; i < n ; i++) {
                if(i%3 == 0) putchar('a');
                if(i%3 == 1) putchar('b');
                if(i%3 == 2) putchar('c');
            }
        }else if(m == 2){
            if(n == 1) printf("a");
            if(n == 2) printf("ab");
            if(n == 3) printf("aab");
            if(n == 4) printf("aabb");
            if(n == 5) printf("aaaba");
            if(n == 6) printf("aaabab");
            if(n == 7) printf("aaababb");
            if(n == 8) printf("aaababbb");
            if(n >= 9){
                string a = "aaaa";
                for(int i = 4; i < n ;){
                    if(i+4<n) {
                        a+="babb";
                        i+=4;
                    }
                    if(i+4>=n) {
                        if(i+1==n) a+="a";
                        if(i+2==n) a+="aa";
                        if(i+3==n) a+="aaa";
                        if(i+4==n) a+="aaaa";
                        break;
                    }
                    if(i+4<n) {
                        a+="aaba";
                        i+=4;
                    }
                    if(i+4>=n) {
                        if(i+1==n) a+="b";
                        if(i+2==n) a+="bb";
                        if(i+3==n) a+="bba";
                        if(i+4==n) a+="bbaa";
                        break;
                    }
                    if(i+4<n) {
                        a+="bbaa";
                        i+=4;
                    }
                    if(i+4>=n) {
                        if(i+1==n) a+="a";
                        if(i+2==n) a+="aa";
                        if(i+3==n) a+="bab";
                        if(i+4==n) a+="babb";
                        break;
                    }
                }
                cout<<a;
            }
        }
        putchar('
');
    }
    return 0;
}