UVA - 247 Calling Circles

#include<bits/stdc++.h>
#define _for(i,a,b) for(int i=a;i<b;i++)
using namespace std;

const int maxn = 25 + 3;
int g[maxn][maxn];
int gg[maxn][maxn];
int g2[maxn][maxn];
int n, m;
map<string, int>id;
map<int,string>name;

int getID(string &s)
{
    if(id.count(s))
        return id[s];
    id[s] = id.size() - 1;
    name[id[s]] = s;
    return id[s];
}

void floyd()
{
    _for(k,0,n)
        _for(i,0,n)
            _for(j,0,n)
                g[i][j] = g[i][j] ? 1: (g[i][k] && g[k][j]);
}

int vis[maxn];
vector<int>ans;
void solve(int s)
{
    vis[s] = 1;
    ans.push_back(s);
    _for(i,0,n){
        if(g2[s][i] && !vis[i]){
            solve(i);
        }
    }
}
int main()
{
//    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);
    int kase = 0;
    while(cin >> n >> m && n){
        id.clear();
        name.clear();
        memset(g, 0, sizeof(g));
        memset(g2, 0, sizeof(g2));
        _for(i,0,n){
            g[i][i] = 1;
        }
        _for(i,0,m){
            string s1, s2;
            cin >> s1 >> s2;
            int id1 = getID(s1);
            int id2 = getID(s2);
            g[id1][id2] = 1;
        }
        memcpy(gg, g, sizeof(gg));
        floyd();
        _for(i,0,n){
            _for(j,0,n){
                if(g[i][j] && g[j][i]){
                    g2[i][j] = g2[j][i] = 1;
                }
            }
        }
        memset(vis, 0, sizeof(vis));
        if(kase != 0){
            cout << endl;
        }
        printf("Calling circles for data set %d:\n", ++kase);
        //if(m != 0)  //如果没有边，不应该输出各个点
        _for(i,0,n){
            ans.clear();
            if(!vis[i]){
                solve(i);
                //如果点没在电话记录里出现过，不应该自成一个圈。或者也可以在下面输出name的时候处理，先判断是否有名字
                int u = ans[0];
                int ok = (ans.size() == 1)? 0 : 1;
                if(ans.size() == 1)
                    _for(i,0,n){
                        if(i != u)
                            if(gg[u][i] || gg[i][u]){
                                ok = 1;
                                break;
                            }
                    }
                if(ok)
                    _for(i,0,ans.size()){
                        if(i == ans.size() - 1) cout << name[ans[i]] << endl;
                        else cout << name[ans[i]] << ", ";
                    }
            }
        }
    }
    return 0;
}