C++_USACO_Broken Necklace

/*
PROB:beads
LANG:C++
*/
#include<iostream>
#include<string>
#include <cstdlib>
#include <cstring>
#include<fstream>
using namespace std;
string strReverse(string str1){
    int len=str1.size();
    string str2=str1;
    char *end=&str1[0]+len-1;
    for(int i=0;i<len;i++)
        if(end>&str1[0]){
            str2[i]=end[0];
            end--;
        }
        else if(end==&str1[0]){
            str2[i]=end[0];
            break;
        }
    return str2;
}
int first_maxLen(string newstr){
    int i=0;
    int n=newstr.size();
    int temp_len=0;
    char br=' ';
    if(newstr[0]=='w'){
        while(i<n){
            if(newstr[i]=='w' || newstr[i]==br){
                temp_len++;
                i++;
                continue;
            }
            if(br==' '){
                br=newstr[i];
                temp_len++;
                i++;
                continue;
            }
            if(br!=newstr[i])
                break;
        }
    }
    else{
        br=newstr[0];
        while(i<n){
            if(newstr[i]==br||newstr[i]=='w'){
                temp_len++;
                i++;
                continue;
            }
            else
                break;
        }
    }
    return temp_len;
}
int main(){
    ifstream ifs("beads.in");
    ofstream ofs("beads.out");
    int n;
    int back_len;
    int forward_len; 
    int new1_firstmax;
    int new2_firstmax;
    int new1_finalmax=0;
    int new2_finalmax=0;
    int max=0;
    int tempmax=0;
    string necklace="";
    ifs>>n;
    if(n>350||n<3)
        return 0;
    ifs>>necklace;
    string reverse_lace=strReverse(necklace);
    new1_finalmax=first_maxLen(necklace);
    new2_finalmax=first_maxLen(reverse_lace);
    if(reverse_lace.compare(necklace)==0){
        max=new1_finalmax;
    }
    else{
        max=new1_finalmax+new2_finalmax;
    }
    string back_str="";
    string forward_str="";
    string newstr1="";
    string newstr2="";
    for(int i=0;i<n-1;i++){
        back_str=&necklace[i+1];
        back_len=back_str.size();
        forward_len=n-back_len;
        forward_str=necklace.substr(0,forward_len);
        newstr1=strcat(&back_str[0],&forward_str[0]);
        newstr2=strReverse(newstr1);
        new1_firstmax=first_maxLen(newstr1);
        new2_firstmax=first_maxLen(newstr2);
        if(newstr1.compare(newstr2)==0)
            tempmax=new1_firstmax;
        else{
            tempmax=new1_firstmax+new2_firstmax;
        }
        if(tempmax>max)
            max=tempmax;
    }
    ofs<<max<<endl;
return 0;
}

代码质量很差，用了很多字符串拷贝，占用过多内存。而且自己电脑上面测试都没有错，但是结果在USACO上面总是错误的。还未解决！可以参考给的答案。发现人家的答案好简单！对比一下。
我的错误如下：

Compiling... Compile: OK
Executing...    Test 1: TEST OK [0.000 secs, 3500 KB]    Test 2: TEST OK [0.000 secs, 3500 KB]    Test 3: TEST OK [0.000 secs, 3500 KB]    Test 4: TEST OK [0.000 secs, 3500 KB]    Test 5: TEST OK [0.000 secs, 3500 KB]

  > Run 6: Execution error: Your program had this runtime error:
        Illegal file open (/dev/tty). The program ran for 0.000 CPU
        seconds before the error. It used 3500 KB of memory. 

        ------ Data for Run 6 [length=11 bytes] ------
        8 
        rrwwwwbb 
        ----------------------------

    Test 6: SIGNAL 50 (0.000 secs, 3500 KB)

人家的代码哦：

#include<fstream>
using namespace std;
 
int main()
{
    int num,max=0,n,i,j,k;
    char *p,symbol1,symbol2;
    ifstream fin("beads.in");
    ofstream fout("beads.out");
 
    fin>>n;
    p=new char[n+1];
    fin>>p;
 
    for(i=n;i<2*n;++i){
        if(p[i%n]!=p[(i+1)%n]){                               
            symbol1=p[i%n]!='w'?p[i%n]:(p[(i+1)%n]=='r'?'b':'r');   
            symbol2=symbol1=='r'?'b':'r';
            num=0;
 
            for(j=i;j>i-n;--j){
                if(p[j%n]==symbol1||p[j%n]=='w') ++num;        
                else break;
            }
            for(k=i+1;k<j+n+1;++k){
                if(p[k%n]==symbol2||p[k%n]=='w') ++num;
                else break;
            }
 
            max=max>num?max:num;                     
        }
    }
 
    if(max==0) max=n;                               
    fout<<max<<endl;
    fin.close();
    fout.close();
    delete [] p;
 
    return 0;
}