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//针对有向图void dfs(int x) {    f[x]=true;    d[x]=low[x]=++Time;    sta.push(x);instack[x]=true;    for (int e=head[x];e!=0;e=next[e]) {        if (!f[vet[e]]) {            dfs(vet[e]);            low[x]=min(low[x],low[vet[e]]);        }        else if (instack[vet[e]]) low[x]=min(low[x],d[vet[e]]);    }    if (low[x]==d[x]) {        idnum++;        while (sta.top()!=x) {            instack[sta.top()]=false;            idc[sta.top()]=idnum;            sta.pop();        }        idc[x]=idnum;        instack[x]=false;        sta.pop();    }}int main() {    int n;    cin >> n;    while (!sta.empty()) sta.pop();    for (int i=1;i<=n;i++)        if (!f[i]) dfs(i);    for (int i=1;i<=n;i++)        for (int e=head[i];e!=0;e=next[e])//遍历每条边            if (idc[i]!=idc[vet[e]]) ind[idc[vet[e]]]++;    return 0;}