LOOP判断单环

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#include <cmath>
#include <map>
using namespace std;
const int maxn = 1010;//点的个数  可以修改  maxn <= 20005即可满足要求
const double pi = 3.141592653589;
struct Point {
    int id;
    int x;
    int y;
};
bool cmp(Point p1, Point p2) {
    if(p1.id != p2.id) return p1.id < p2.id;
}

class Loop {
public:
    int n;
    int G[maxn][maxn];
    vector<int> V[maxn];
    Point init[maxn], point[maxn], ans[maxn];
    map<string, int> mp;

    void Init(int n) {
        this -> n = n;
        for(int i = 1; i <= n; i++) {
            V[i].clear();
        }
        mp.clear();
        memset(G, 0, sizeof(G));
    }

    void input() {
        for(int i = 1; i <= n; i++) {
            scanf("%d %d %d",&init[i].id, &init[i].x, &init[i].y);
        }
        int u, v;
        for(int i = 1; i <= n; i++) {
            scanf("%d",&u);
            for(int j = 1; j <= 4; j++) {
                scanf("%d",&v);
                if(v != 0) {
                    G[u][v] = G[v][u] = 1;
                    V[u].push_back(v);
                }
            }
        }
    }

    void check(Point a[maxn], int cnt) {
        if(cnt < 3) return ;
        Point b[maxn];
        for(int i = 0; i < cnt; i++) {
            b[i] = a[i];
        }
        sort(b, b + cnt, cmp);
        string s;
        for(int i = 0; i < cnt; i++) {
            char str[10];
            sprintf(str, "%d", b[i].id);
            s += str;
        }
        s += '';
        if(!mp[s]) {
            mp[s] = 1;
            for(int i = 0; i < cnt; i++) {
                printf("%d ", a[i].id);
            } puts("");
        }
    }

    double C(Point p0, Point p1, Point p2) {
        double x1 = p1.x - p0.x; double y1 = p1.y - p0.y;
        double x2 = p2.x - p0.x; double y2 = p2.y - p0.y;
        double a = sqrt( x1*x1 + y1*y1 );
        double b = sqrt( x2*x2 + y2*y2 );
        double ab = x1*x2 + y1*y2;
        double caob = ab / ( a * b );
        double jiaodu = acos(caob);
        return jiaodu / pi * 180 + 1e-6;
    }
    double D(Point p0, Point p1, Point p2) {
        double x1 = p1.x - p0.x; double y1 = p1.y - p0.y;
        double x2 = p2.x - p0.x; double y2 = p2.y - p0.y;
        double ans = x1 * y2 - x2 * y1;
        return ans;
    }
    int eps(double x) {
        if(fabs(x) < 1e-8) return 0;
        if(x < 0) return -1;
        return 1;
    }

    void solve() {
        for(int i = 1; i <= n; i++) {
            for(int j = 1; j <= n; j++) {
                if(i == j) continue;
                if(!G[i][j]) continue;
                int vis[maxn] = { 0 };
                int cnt = 1;
                vis[i] = vis[j] = 1;
                point[cnt++] = init[i];
                point[cnt++] = init[j];
                int num = n - 2;
                while(num--) {
                    double ang = 181;
                    int id_num = n + 1;
                    int now = point[cnt - 1].id;
                    bool fla = false;
                    for(int k = 0; k < V[now].size(); k++) {
                        int u = V[now][k];
                        if(vis[u]) continue;
                        double a1 = D(point[cnt - 1], point[cnt - 2], init[u]);
                        if(eps(a1) >= 0) {
                            double a2 = C(point[cnt - 1], point[cnt - 2], init[u]);
                            if(ang > a2) {
                                ang = a2;
                                id_num = u;
                            }
                        }
                    }
                    if(id_num <= n) {
                        fla = true;
                        point[cnt++] = init[id_num];
                        vis[id_num] = 1;
                    } else {
                        double ang2 = -1;
                        int id_num2 = n + 1;
                        for(int k = 0; k < V[now].size(); k++) {
                            int u = V[now][k];
                            if(vis[u]) continue;
                            double a1 = D(point[cnt - 1], point[cnt - 2], init[u]);
                            if(eps(a1) < 0) {
                                double a2 = C(point[cnt - 1], point[cnt - 2], init[u]);
                                if(ang < a2) {
                                    ang2 = a2;
                                    id_num2 = u;
                                }
                            }
                        }
                        if(id_num2 <= n) {
                            fla = true;
                            point[cnt++] = init[id_num2];
                            vis[id_num2] = 1;
                        }
                    }
                    if(!fla) break;
                    bool flag = false;
                    for(int l = cnt - 3; l >= 1; l--) {
                        if(G[point[l].id][id_num]) {
                            flag = true;
                            int cnt_1 = 0;
                            for(int ll = l; ll < cnt; ll++) {
                                ans[cnt_1++] = point[ll];
                            }
                            check(ans, cnt_1);
                            break;
                        }
                    }
                    if(flag) {
                        break;
                    }
                }
            }
        }
    }
};
Loop l1;

int main() {
    int n;
    freopen("in.txt","r",stdin);
    while(EOF != scanf("%d",&n) ) {
        l1.Init(n);
        l1.input();
        l1.solve();
    }
    return 0;
}