ADDED   SRM/516-U/2A.cpp
Index: SRM/516-U/2A.cpp
==================================================================
--- SRM/516-U/2A.cpp
+++ SRM/516-U/2A.cpp
@@ -0,0 +1,100 @@
+#include <iostream>
+#include <sstream>
+#include <iomanip>
+#include <vector>
+#include <string>
+#include <map>
+#include <set>
+#include <algorithm>
+#include <numeric>
+#include <iterator>
+#include <functional>
+#include <complex>
+#include <queue>
+#include <stack>
+#include <cmath>
+#include <cassert>
+#include <cstring>
+using namespace std;
+typedef long long LL;
+typedef complex<double> CMP;
+
+class NetworkXZeroOne { public:
+	string reconstruct(string message)
+	{
+		if( message[0]=='?' ) {
+			string msg = message;
+			msg[0] = 'o';
+			if( check(msg) )
+				return msg;
+			message[0] = 'x';
+		}
+		check(message);
+		return message;
+	}
+
+	bool check(string& msg)
+	{
+		for(int i=1; i<msg.size(); ++i)
+			if( msg[i]=='?' ) {
+				if( msg[i-1]=='x' )
+					msg[i]='o';
+				else
+					msg[i]='x';
+			}
+		for(int i=0; i<msg.size(); ++i)
+			for(int k=2; i+k<=msg.size(); k+=2)
+				if( count(msg.begin()+i, msg.begin()+i+k, 'o')*2 != k )
+					return false;
+		return true;
+	}
+};
+
+// BEGIN CUT HERE
+#include <ctime>
+double start_time; string timer()
+ { ostringstream os; os << " (" << int((clock()-start_time)/CLOCKS_PER_SEC*1000) << " msec)"; return os.str(); }
+template<typename T> ostream& operator<<(ostream& os, const vector<T>& v)
+ { os << "{ ";
+   for(typename vector<T>::const_iterator it=v.begin(); it!=v.end(); ++it)
+   os << '\"' << *it << '\"' << (it+1==v.end() ? "" : ", "); os << " }"; return os; }
+void verify_case(const string& Expected, const string& Received) {
+ bool ok = (Expected == Received);
+ if(ok) cerr << "PASSED" << timer() << endl;  else { cerr << "FAILED" << timer() << endl;
+ cerr << "\to: \"" << Expected << '\"' << endl << "\tx: \"" << Received << '\"' << endl; } }
+#define CASE(N) {cerr << "Test Case #" << N << "..." << flush; start_time=clock();
+#define END	 verify_case(_, NetworkXZeroOne().reconstruct(message));}
+int main(){
+
+CASE(0)
+	string message = "x?x?"; 
+	string _ = "xoxo"; 
+END
+CASE(1)
+	string message = "?xo?"; 
+	string _ = "oxox"; 
+END
+CASE(2)
+	string message = "xo"; 
+	string _ = "xo"; 
+END
+CASE(3)
+	string message = "o??x??o"; 
+	string _ = "oxoxoxo"; 
+END
+CASE(4)
+	string message = "???????x"; 
+	string _ = "oxoxoxox"; 
+END
+/*
+CASE(5)
+	string message = ; 
+	string _ = ; 
+END
+CASE(6)
+	string message = ; 
+	string _ = ; 
+END
+*/
+}
+// END CUT HERE

ADDED   SRM/516-U/2B.cpp
Index: SRM/516-U/2B.cpp
==================================================================
--- SRM/516-U/2B.cpp
+++ SRM/516-U/2B.cpp
@@ -0,0 +1,125 @@
+#include <iostream>
+#include <sstream>
+#include <iomanip>
+#include <vector>
+#include <string>
+#include <map>
+#include <set>
+#include <algorithm>
+#include <numeric>
+#include <iterator>
+#include <functional>
+#include <complex>
+#include <queue>
+#include <stack>
+#include <cmath>
+#include <cassert>
+#include <cstring>
+using namespace std;
+typedef long long LL;
+typedef complex<double> CMP;
+
+class NetworkXOneTimePad { public:
+	int crack(vector <string> plaintexts, vector <string> ciphertexts)
+	{
+		set<string> possible_keys;
+		for(int i=0; i<plaintexts.size(); ++i)
+			for(int j=0; j<ciphertexts.size(); ++j)
+				possible_keys.insert(key(plaintexts[i], ciphertexts[j]));
+
+		int cnt = 0;
+		for(set<string>::iterator it=possible_keys.begin(); it!=possible_keys.end(); ++it)
+		{
+			const string& key = *it;
+			set<string> target(plaintexts.begin(), plaintexts.end());
+			for(int i=0; i<ciphertexts.size(); ++i) {
+				string ci = cipher(ciphertexts[i], key);
+				if( !target.count(ci) )
+					goto next;
+				target.erase(ci);
+			}
+			++cnt;
+		next:;
+		}
+		return cnt;
+	}
+
+	string cipher(const string& a, const string& b)
+	{
+		string c;
+		for(int i=0; i<a.size(); ++i)
+			c += char(a[i]^(b[i]=='1'));
+		return c;
+	}
+
+	string key(const string& a, const string& b)
+	{
+		string c;
+		for(int i=0; i<a.size(); ++i)
+			c += (a[i]==b[i] ? '0' : '1');
+		return c;
+	}
+};
+
+// BEGIN CUT HERE
+#include <ctime>
+double start_time; string timer()
+ { ostringstream os; os << " (" << int((clock()-start_time)/CLOCKS_PER_SEC*1000) << " msec)"; return os.str(); }
+template<typename T> ostream& operator<<(ostream& os, const vector<T>& v)
+ { os << "{ ";
+   for(typename vector<T>::const_iterator it=v.begin(); it!=v.end(); ++it)
+   os << '\"' << *it << '\"' << (it+1==v.end() ? "" : ", "); os << " }"; return os; }
+void verify_case(const int& Expected, const int& Received) {
+ bool ok = (Expected == Received);
+ if(ok) cerr << "PASSED" << timer() << endl;  else { cerr << "FAILED" << timer() << endl;
+ cerr << "\to: \"" << Expected << '\"' << endl << "\tx: \"" << Received << '\"' << endl; } }
+#define CASE(N) {cerr << "Test Case #" << N << "..." << flush; start_time=clock();
+#define END	 verify_case(_, NetworkXOneTimePad().crack(plaintexts, ciphertexts));}
+int main(){
+
+CASE(0)
+	string plaintexts_[] = {"110", "001"};
+	  vector <string> plaintexts(plaintexts_, plaintexts_+sizeof(plaintexts_)/sizeof(*plaintexts_)); 
+	string ciphertexts_[] = {"101", "010"};
+	  vector <string> ciphertexts(ciphertexts_, ciphertexts_+sizeof(ciphertexts_)/sizeof(*ciphertexts_)); 
+	int _ = 2; 
+END
+CASE(1)
+	string plaintexts_[] = {"00", "01", "10", "11"};
+	  vector <string> plaintexts(plaintexts_, plaintexts_+sizeof(plaintexts_)/sizeof(*plaintexts_)); 
+	string ciphertexts_[] = {"00", "01", "10", "11"};
+	  vector <string> ciphertexts(ciphertexts_, ciphertexts_+sizeof(ciphertexts_)/sizeof(*ciphertexts_)); 
+	int _ = 4; 
+END
+CASE(2)
+	string plaintexts_[] = {"01", "10"};
+	  vector <string> plaintexts(plaintexts_, plaintexts_+sizeof(plaintexts_)/sizeof(*plaintexts_)); 
+	string ciphertexts_[] = {"00"};
+	  vector <string> ciphertexts(ciphertexts_, ciphertexts_+sizeof(ciphertexts_)/sizeof(*ciphertexts_)); 
+	int _ = 2; 
+END
+CASE(3)
+	string plaintexts_[] = {"000", "111", "010", "101", "110", "001"};
+	  vector <string> plaintexts(plaintexts_, plaintexts_+sizeof(plaintexts_)/sizeof(*plaintexts_)); 
+	string ciphertexts_[] = {"011", "100"};
+	  vector <string> ciphertexts(ciphertexts_, ciphertexts_+sizeof(ciphertexts_)/sizeof(*ciphertexts_)); 
+	int _ = 6; 
+END
+/*
+CASE(4)
+	string plaintexts_[] = ;
+	  vector <string> plaintexts(plaintexts_, plaintexts_+sizeof(plaintexts_)/sizeof(*plaintexts_)); 
+	string ciphertexts_[] = ;
+	  vector <string> ciphertexts(ciphertexts_, ciphertexts_+sizeof(ciphertexts_)/sizeof(*ciphertexts_)); 
+	int _ = ; 
+END
+CASE(5)
+	string plaintexts_[] = ;
+	  vector <string> plaintexts(plaintexts_, plaintexts_+sizeof(plaintexts_)/sizeof(*plaintexts_)); 
+	string ciphertexts_[] = ;
+	  vector <string> ciphertexts(ciphertexts_, ciphertexts_+sizeof(ciphertexts_)/sizeof(*ciphertexts_)); 
+	int _ = ; 
+END
+*/
+}
+// END CUT HERE

ADDED   SRM/516-U/2C.cpp
Index: SRM/516-U/2C.cpp
==================================================================
--- SRM/516-U/2C.cpp
+++ SRM/516-U/2C.cpp
@@ -0,0 +1,98 @@
+#include <iostream>
+#include <sstream>
+#include <iomanip>
+#include <vector>
+#include <string>
+#include <map>
+#include <set>
+#include <algorithm>
+#include <numeric>
+#include <iterator>
+#include <functional>
+#include <complex>
+#include <queue>
+#include <stack>
+#include <cmath>
+#include <cassert>
+#include <cstring>
+using namespace std;
+typedef long long LL;
+typedef complex<double> CMP;
+
+class NetworkXMessageRecovery { public:
+	string recover(vector <string> messages)
+	{
+		map< char, set<char> > prev;
+		for(int i=0; i<messages.size(); ++i) {
+			prev[messages[i][0]];
+			for(int j=0; j+1<messages[i].size(); ++j)
+				prev[messages[i][j+1]].insert(messages[i][j]);
+		}
+
+		string result;
+		while( !prev.empty() )
+		{
+			set<char> cand;
+			for(map< char,set<char> >::iterator it=prev.begin(); it!=prev.end(); ++it)
+				if( it->second.empty() )
+					cand.insert(it->first);
+			char c = *cand.begin();
+			result += c;
+			for(map< char,set<char> >::iterator it=prev.begin(); it!=prev.end(); ++it)
+				it->second.erase(c);
+			prev.erase(c);
+		}
+		return result;
+	}
+};
+
+// BEGIN CUT HERE
+#include <ctime>
+double start_time; string timer()
+ { ostringstream os; os << " (" << int((clock()-start_time)/CLOCKS_PER_SEC*1000) << " msec)"; return os.str(); }
+template<typename T> ostream& operator<<(ostream& os, const vector<T>& v)
+ { os << "{ ";
+   for(typename vector<T>::const_iterator it=v.begin(); it!=v.end(); ++it)
+   os << '\"' << *it << '\"' << (it+1==v.end() ? "" : ", "); os << " }"; return os; }
+void verify_case(const string& Expected, const string& Received) {
+ bool ok = (Expected == Received);
+ if(ok) cerr << "PASSED" << timer() << endl;  else { cerr << "FAILED" << timer() << endl;
+ cerr << "\to: \"" << Expected << '\"' << endl << "\tx: \"" << Received << '\"' << endl; } }
+#define CASE(N) {cerr << "Test Case #" << N << "..." << flush; start_time=clock();
+#define END	 verify_case(_, NetworkXMessageRecovery().recover(messages));}
+int main(){
+
+CASE(0)
+	string messages_[] = {"acd", "bce"};
+	  vector <string> messages(messages_, messages_+sizeof(messages_)/sizeof(*messages_)); 
+	string _ = "abcde"; 
+END
+CASE(1)
+	string messages_[] = {"ed", "dc", "cb", "ba"};
+	  vector <string> messages(messages_, messages_+sizeof(messages_)/sizeof(*messages_)); 
+	string _ = "edcba"; 
+END
+CASE(2)
+	string messages_[] = {"Fox", "Ciel", "FoxCiel"};
+	  vector <string> messages(messages_, messages_+sizeof(messages_)/sizeof(*messages_)); 
+	string _ = "FoxCiel"; 
+END
+CASE(3)
+	string messages_[] = {"a", "A"};
+	  vector <string> messages(messages_, messages_+sizeof(messages_)/sizeof(*messages_)); 
+	string _ = "Aa"; 
+END
+/*
+CASE(4)
+	string messages_[] = ;
+	  vector <string> messages(messages_, messages_+sizeof(messages_)/sizeof(*messages_)); 
+	string _ = ; 
+END
+CASE(5)
+	string messages_[] = ;
+	  vector <string> messages(messages_, messages_+sizeof(messages_)/sizeof(*messages_)); 
+	string _ = ; 
+END
+*/
+}
+// END CUT HERE