HDU 1200 字符串

#include<iostream>#include<string>#include<cstring>#include<algorithm>#include<cstdio>#include<cmath>#include<cctype>using namespace std;int main() {    int n;    while(cin>>n&&n) {        string s; cin>>s;        string f[1000];        int a=0,j;        for(j=0; a+n<=s.size(); j++,a+=n) {            f[j].assign(s,a,n);            if(j%2)reverse(f[j].begin(),f[j].end());        }        if(a<s.size()-1){            int l=s.size()-a;            f[j].assign(s,a,l);            ++j;        }        for(int i=0,k;i<n;++i)            for(k=0;k<j;k++)                cout<<f[k][i];        cout<<endl;    }    return 0;}