POJ 3617 Best Cow Line 贪心

不能单纯比较头尾两个字符，应该比较头尾两个字符串。

//#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<iostream>
#include<sstream>
#include<cmath>
#include<climits>
#include<string>
#include<map>
#include<queue>
#include<vector>
#include<stack>
#include<set>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
#define pb(a) push(a)
#define INF 0x1f1f1f1f
#define lson idx<<1,l,mid
#define rson idx<<1|1,mid+1,r
#define PI  3.1415926535898
template<class T> T min(const T& a,const T& b,const T& c) {
    return min(min(a,b),min(a,c));
}
template<class T> T max(const T& a,const T& b,const T& c) {
    return max(max(a,b),max(a,c));
}
void debug() {
#ifdef ONLINE_JUDGE
#else

    freopen("in.txt","r",stdin);
    //freopen("d:\\out1.txt","w",stdout);
#endif
}
int getch() {
    int ch;
    while((ch=getchar())!=EOF) {
        if(ch!=' '&&ch!='\n')return ch;
    }
    return EOF;
}

const int maxn=2005;
char s[maxn];
int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        for(int i=0;i<n;i++)
            scanf(" %c",&s[i]);
        int l=0,r=n-1;
        for(int i=0;i<n;i++)
        {
            int a=l,b=r;
            while(a<b&&s[a]==s[b])a++,b--;
            if(s[a]<s[b])
            {
                printf("%c",s[l]);l++;
            }else
            {
                printf("%c",s[r]);r--;
            }
            if((i+1)%80==0)printf("\n");
        }
        if(n%80!=0)printf("\n");
    }
    return 0;
}