USACO 1.3 Calf Flac(枚举）

枚举+标记即可。

/*

 ID: cuizhe

 LANG: C++

 TASK: calfflac

*/

#include <iostream>

#include <cstdio>

#include <cstring>

#include <cstdlib>

#include <map>

#include <algorithm>

using namespace std;

char str[30001],p[30001];

int o[30001];

int main()

{

    int i,j,len,num,ans,t1,t2,st,end;

    char ch;

    freopen("calfflac.in","r",stdin);

    freopen("calfflac.out","w",stdout);

    i = 0;

    while(scanf("%c",&ch)!=EOF)

    {

        str[i] = ch;

        i ++;

    }

    len = i-1;j = 0;

    for(i = 0;i <= len;i ++)

    {

        if(str[i] <= 'z'&&str[i] >= 'a')

        {

            o[j] = i;

            p[j++] = str[i];

        }

        else if(str[i] <= 'Z'&&str[i] >= 'A')

        {

            o[j] = i;

            p[j++] = str[i] + 32;

        }

    }

    num = j-1;ans = 0;

    for(i = 0;i <= num;i ++)

    {

        int temp = 0;

        st = i-1;

        end = i;

        while(st >= 0&&end <= num)

        {

            if(p[st] == p[end])

            temp += 2;

            else

            break;

            st --;

            end ++;

        }

        if(ans < temp)

        {

            ans = temp;

            t1 = o[st+1];

            t2 = o[end-1];

        }

        temp = 1;

        st = i-1;

        end = i+1;

        while(st >= 0&&end <= num)

        {

            if(p[st] == p[end])

            temp += 2;

            else

            break;

            st --;

            end ++;

        }

        if(ans < temp)

        {

            ans = temp;

            t1 = o[st+1];

            t2 = o[end-1];

        }

    }

    printf("%d\n",ans);

    for(i = t1;i <= t2;i ++)

    {

        printf("%c",str[i]);

    }

    printf("\n");

    return 0;

}