UVa247 - Calling Circles

#include <cstdio>
#include <iostream>
#include <fstream>
#include <string>
#include <map>
#include <cstring>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;

const int N = 30;

map<string, int> strMap;
map<int, string> intMap;

int idx(string &s);
int f

;
int dfn
, low
;
int dfsclock;
stack<int> s;
int n, m;
bool inStack
;

void Tarjan(int u);

int main()
{
string s1, s2;
int t = 1;

#ifndef ONLINE_JUDGE
//freopen("d:\\OJ\\uva_in.txt", "r", stdin);
ifstream cin("d:\\OJ\\uva_in.txt");
#endif

while (cin >> n >> m) {
if (n == 0 && m == 0) break;
memset(f, 0x00, sizeof(f));
strMap.clear();
intMap.clear();
while (m--) {
cin >> s1 >> s2;
int u = idx(s1), v = idx(s2);
f[u][v] = 1;
}

memset(dfn, 0x00, sizeof(dfn));
memset(low, 0x00, sizeof(low));
memset(inStack, false, sizeof(inStack));
while (!s.empty()) s.pop();
dfsclock = 0;

if (t > 1) cout << endl;

cout << "Calling circles for data set " << t++ << ":" << endl;
for (int i = 0; i < n; i++) {
if (!dfn[i]) Tarjan(i);
}

}
return 0;
}

int idx(string &s)
{
if (strMap.count(s)) return strMap[s];
int size = strMap.size();

strMap[s] = size;
intMap[size] = s;
return size;
}

void Tarjan(int u)
{
dfn[u] = low[u] = ++dfsclock;
s.push(u);
inStack[u] = true;

for (int v = 0; v < n; v++) {
if (f[u][v] && !dfn[v]) {
Tarjan(v);
low[u] = min(low[u], low[v]);
} else if (f[u][v] && inStack[v]) {
low[u] = min(low[u], dfn[v]);
}
}

if (dfn[u] == low[u]) {
vector<int> intVec;
while (!s.empty()) {
int v = s.top(); s.pop();
inStack[v] = false;
intVec.push_back(v);
if (v == u) break;
}

for (size_t i = 0; i < intVec.size(); i++) {
if (i) cout << ", ";
cout << intMap[intVec[i]];
}
cout << endl;
}
}