ACM Topic ———— Difficult string

Title Description

If a string contains two contiguous repeating substrings, it is called an "easy string", and the other strings are called "difficult strings". For example, BB,ABCDACABCAB,ABCDABCD are easy strings, and D,dc,abdab,cbabcbad are difficult strings.

Input

Enter positive integers n and L.

Output

The output consists of a string of the first L strings, a dictionary order K small difficult string. For example, when L=3, the first 7 difficult strings were a,ab,aba,abac,abaca,abacab,abacaba. Enter a guaranteed answer of no more than 80 characters.

Sample input

7 330 3

Sample output

Abacabaabacabcacbabcabacabcacbacaba

Success on the small white knocked once, but the egg, do not know the problem.

Difficult string # include <iostream> #include <string.h> #include <stdio.h>using namespace Std;int N, s[1001], L, Cnt;int DFS (int cur) {    if (cnt + = = N)    {        for (int i=0; i<cur; i++) printf ("%c", ' A ' +s[i]);        printf ("\ n");        return 0;    }    for (int i=0; i<l; i++)    {        S[cur] = i;        int OK = 1;        for (int j=1; j*2<=cur+1; j + +)        {            int e = 1;            for (int k=0; k<j; k++)                if (s[cur-k]! = S[cur-k-j])                {                    e = 0;                    break;                }            if (e)            {                OK = 0;                break;            }        }        if (OK) if (! DFS (cur+1)) return 0;    }    return 1;} int main () {while    (~scanf ("%d%d", &n, &l))    {        cnt = 0;        Memset (s,0,sizeof (s));        DFS (0);    }    return 0;}

ACM Topic ———— Difficult string