usaco 1.3 calfflac...枚举...

/*
    ID:chenjiong
    PROG:calfflac
    LANG:C++
*/

#include <stdio.h>
#include <string.h>
#include <iostream>

using namespace std;

char txt[20005];
int len;

typedef struct {
    int l;
    int r;
    int mid;
    int length;
}NODE;

NODE final;
NODE tmp;

bool is_same(char a,char b)
{
    if ( a == b || a - b == 'A' - 'a' || b - a == 'A' - 'a' )
        return true;
    return false;
}

void find_odd(int cur,NODE& t)
{
    if ( !isalpha(txt[cur]) )
        return;
    
    t.mid = cur;
    t.length = 1;
    t.l = t.r = cur;
    
    int i = cur - 1;
    int j = cur + 1;
    while ( i >= 0 && j <= len - 1 )
    {
        if ( !isalpha(txt[i]) )
        {
            i--;
            continue;
        }
        if ( !isalpha(txt[j]) )
        {
            j++;
            continue;
        }
        if ( !is_same(txt[i],txt[j]) )
            return;

        t.l = i--;
        t.r = j++;
        t.length += 2;
    }
}

void find_even(int cur,NODE& t)
{
    if ( !isalpha(txt[cur]) )
        return;
    int i = cur;
    int j = cur + 1;
    while ( j <= len - 1 )
    {
        if ( !isalpha(txt[j]) )
            j++;
        else 
            break;
    }

    if ( !is_same(txt[i],txt[j]) )
        return;

    t.l = i;
    t.r = j;
    t.length = 2;
    t.mid = cur;
    i--;
    j++;
    while ( i >= 0 && j <= len - 1 )
    {
        if ( !isalpha(txt[i]) )
        {
            i--;
            continue;
        }
        if ( !isalpha(txt[j]) )
        {
            j++;
            continue;
        }
        if ( !is_same(txt[i],txt[j]) )
            return;

        t.l = i--;
        t.r = j++;
        t.length += 2;
    }
}

int main()
{
    freopen("calfflac.in","r",stdin);
    freopen("calfflac.out","w",stdout);

    cin.getline(txt,20000,'\0');
    len = strlen(txt);

//    printf("%s\n",txt);

    int i;
    for ( i = 0; i < len; i++)
    {
        find_even(i,tmp);
        if ( tmp.length > final.length )
            final = tmp;
        
        find_odd(i,tmp);
        if ( tmp.length > final.length )
            final = tmp;
    }

    txt[final.r + 1] = '\0';
    printf("%d\n",final.length);
    printf("%s\n",&txt[final.l]);

    return 0;
}