这个&有什么用，不加的话死循环，求助大佬

#include <bits/stdc++.h>//Dinic最大流
using namespace std;
struct edge {
    int to, cap, rev;
};
vector<edge> g[100000];
int l[100000];
int it[100000];
int n, m, s, t;
void bfs(int x)
{
    memset(l, -1, sizeof(l));
    queue<int> q;
    l[x] = 0;
    q.push(x);
    while (q.size())
    {
        int v = q.front();
        q.pop();
        for (int i = 0; i < g[v].size(); i++)
        {
            edge e = g[v][i];
            if (e.cap > 0 && l[e.to] < 0)
            {
                l[e.to] = l[v] + 1;
                q.push(e.to);
            }
        }
    }
}
int dfs(int v, int w, int f)
{
    if (v == w)
        return f;
    for (int i = it[v]; i < g[v].size(); i++)
    {

        edge    &e= g[v][i];
        if (e.cap > 0 && l[v] < l[e.to])
        {
            int d = dfs(e.to, t, min(f, e.cap));
            if (d > 0)
            {
                e.cap -= d;
                g[e.to][e.rev].cap += d;
                return d;
            }
        }
    }
    return 0;
}
int flow(int x, int y)
{
    int flow = 0;
    while (1)
    {
        bfs(x);
        if (l[y] < 0)
            return flow;
        memset(it, 0, sizeof(it));
        int f=0;
        while ((f = dfs(x, y, 1e7)) > 0)
            flow += f;
    }
}
int main()
{
    cin >> n >> m >> s >> t;
    while (m--)
    {
        int qq, ww, ee;
        cin >> qq >> ww >> ee;
        g[qq].push_back({ ww, ee, (int)g[ww].size() });
        g[ww].push_back({ qq, 0, (int)g[qq].size()-1});
    }
    cout << flow(s, t);
}

dfs里面的edge &e= g[v][i];