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#include <iostream> #include <algorithm> #include <queue> #include <vector> #include <cstdlib> #include <cstdio> #include <string> #include <cstring> #include <ctime> #include <iomanip> #include <cmath> #include <set> #include <map> using namespace std; int main(){ map<string, string> id; int num = 0; cin >> num; while (num--) { string oldid,newid; cin >> oldid >> newid; bool flag = false; map<string,string>::iterator it; for (it = id.begin(); it != id.end(); it++) { if ((*it).second == oldid) { flag = true; (*it).second = newid; break; } } if (!flag) { id[oldid] = newid; } } cout << id.size() << endl; map<string,string>::iterator it; for (it = id.begin(); it != id.end(); it++) { cout << (*it).first << ' ' << (*it).second << endl; } return 0; } |
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