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uva00247.cpp
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uva00247.cpp
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#include <iostream>
#include <vector>
#include <cstring>
#include <string>
#include <algorithm>
#include <map>
#include <climits>
#include <cmath>
#include <set>
#include <bitset>
#include <sstream>
#include <iomanip>
#define _ ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0), cout.precision(15);
#define UNVISITED -1
using namespace std;
int n, m, dfsCounter, id1, id2;
vector<string> names;
vector<int> dfs_num, dfs_low, stack;
vector<bool> visiting;
vector< vector<int> > AdjList;
string a, b;
map<string, int> name2id;
void SCC(int p){
dfs_num[p] = dfs_low[p] = dfsCounter++;
visiting[p] = true;
stack.push_back(p);
int q;
for(int i = 0; i < AdjList[p].size(); ++i){
q = AdjList[p][i];
// if(dfs_num[q] == UNVISITED) SCC(q);
// if(visiting[q]) dfs_low[p] = min(dfs_low[p], dfs_low[q]);
// This implementation has a better strucutre of the idea behind the algorithm
if(dfs_num[q] == UNVISITED){
SCC(q);
dfs_low[p] = min(dfs_low[p], dfs_low[q]);
} else if(visiting[q]){
dfs_low[p] = min(dfs_low[p], dfs_num[q]);
}
}
if(dfs_low[p] == dfs_num[p]){
while(true){
q = stack.back();
stack.pop_back();
visiting[q] = false;
if(q != p){
cout << names[q] << ", ";
} else {
cout << names[q] << endl;
break;
}
}
}
}
int main(){ _
int tc = 0;
while(cin >> n >> m){
if(n + m == 0) break;
if(tc) cout << endl;
cout << "Calling circles for data set " << ++tc << ":" << endl;
dfsCounter = 0;
dfs_num.assign(n, UNVISITED);
dfs_low.assign(n, UNVISITED);
visiting.assign(n, false);
AdjList.assign(n, vector<int> (0));
stack.clear();
name2id.clear();
names.clear();
for(int i = 0; i < m; ++i){
cin >> a >> b;
if(name2id.count(a)){
id1 = name2id[a];
} else {
id1 = name2id.size();
name2id[a] = id1;
names.push_back(a);
}
if(name2id.count(b)){
id2 = name2id[b];
} else {
id2 = name2id.size();
name2id[b] = id2;
names.push_back(b);
}
AdjList[id1].push_back(id2);
}
for(int i = 0; i < n; ++i){
if(dfs_num[i] == UNVISITED) SCC(i);
}
}
return 0;
}