#include <algorithm>#include <iostream>#include <cstring>#include <cstdio>#include <vector>#include <queue>#define INF 405#define inf 0x0f0f0f0fusing namespace std;vector <int> vec[INF], ans[INF], id[INF];int Dis[INF], vis[INF];void _addedge(int i, int j, int n){vec[i].push_back(j); id[i].push_back(n);}int bfs(int s, int e){int i, j, t;queue <int> q;memset(vis, 0, sizeof(vis));memset(Dis, 0, sizeof(Dis));for (q.push(s), vis[s]=1; q.empty()==0; ){i=q.front(), q.pop();int siz=vec[i].size(), d=Dis[i];for (j=0; j<siz; j++){ if (t=vec[i][j], vis[t]==0)q.push(t), vis[t]=1, Dis[t]=d+1;if (Dis[t]==d+1) ans[d+1].push_back(id[i][j]);}}return Dis[e];}int main(){int i, j, h, t;for (h=scanf("%d", &t); h<=t; h++){if (h>1) puts("");int n, m, st, et;scanf("%d%d%d%d", &n, &m, &st, &et);for (i=1; i<=n; i++) vec[i].clear(), ans[i].clear(), id[i].clear();for (i=1; i<=m; i++){int x, y;scanf("%d%d", &x, &y);_addedge(x, y, i); _addedge(y, x, i);}int cnt=bfs(st, et);printf("%dn", cnt);for (i=1; i<=cnt; i++){printf("%d", ans[i].size());for (j=0; j<ans[i].size(); j++) printf(" %d", ans[i][j]);puts("");}}return 0;}
