把代码中的emplace_back 替换成push_back，代码的输出不会改变。

#include <bits/stdc+++.h>
using namespace std;
vector<int> v[10005];
int dis[1005], n;
int bfs(int s){
    memset(dis, 0x3f, sizeof(dis));
    queue<int> q;
    q.push(s); dis[s] = 0;
    int ans = 0;
    while (!q.empty()){
        int x = q.front(); q.pop();
        for (int i = 0; i < v[x].size(); i++){
            if (dis[v[x][i]] > dis[x] + 1){
                ans = dis[v[x][i]] = dis[x] + 1;
                q.push(v[x][i]);
            }
        }
    }
    return ans;
}

int main() {
    scanf("%d", &n);
    for (int i = 1; i < n; i++){
        int a, b;
        scanf("%d%d", &a, &b);
        v[a].emplace_back(b);
        v[b].emplace_back(a);
    }
    for (int i = 1; i <= n; i++){
        printf("%d ", bfs(i));
    }
    return 0;
}