[ACM] POJ 3087 Shuffle'm Up

#include<iostream>
#include<string>
#include<map>

using namespace std;

const int MAXDATA = 100000;

map<string, bool> vis;

void shuffle(string &r, string &s1, string &s2) {
r.clear();
string::iterator iter, jter;
for (iter = s1.begin(), jter = s2.begin(); iter != s1.end(); ++iter, ++jter) {
r += *jter;
r += *iter;
}

}

void update(string t, string &s1, string &s2) {
s1.clear(); s2.clear();
size_t jg = t.size();
for (int i = 0; i < jg / 2; i++) {
s1 += t[i];
}
for (int i = jg / 2; i < jg; i++) {
s2 += t[i];
}
}

int main() {
int __;
cin >> __;
for (int i = 1; i <= __; i++) {
string s1, s2, des;
string t;
int trash;
cin >> trash >> s1 >> s2 >> des;
int R = 0;
while (++R) {
shuffle(t, s1, s2);
if (t == des)
break;
if (vis.find(t) != vis.end()) {
R = -1;
break;
}
vis[t] = true;
update(t, s1, s2);
}
cout << i << " " << R << endl;
}
return 0;
}