南陽理工OJ_題目20 吝嗇的國度

#include <iostream>
#include <vector>
#include <cstring>
#include <queue>


using namespace std;

void bfs();

struct data
{
    int vis;
    int f;
};

vector<int> g[100010];
int n;
int s;
data a[100010];
queue<int> q;

int main()
{
    int T;
    cin >> T;
    while(T--)
    {
        cin >> n >> s;
        for(int i = 1; i <= n; i++)
            g[i].clear();
        for(int i = 1; i < n; i++)
        {
            int a, b;
            cin >> a >> b;
            g[a].push_back(b);
            g[b].push_back(a);
        }
        memset(a, 0, sizeof(a));
        bfs();
        for(int i = 1; i <= n; i++)
        {
            if(i == 1)
                cout << a[i].f;
            else
                cout << ' ' << a[i].f;
        }
        cout << '\n';
    }
}

void bfs()
{
    int t;
    a[s].f = -1;
    a[s].vis = 1;
    q.push(s);
    while(!q.empty())
    {
        t = q.front();
        q.pop();
        for(int i = 0; i < g[t].size(); i++)
        {
            if(a[g[t][i]].vis == 0)
            {
                q.push(g[t][i]);
                a[g[t][i]].vis = 1;
                a[g[t][i]].f = t;
            }
        }
    }

}