SPOJ: Submerging Islands

#include <bits/stdc++.h>

using namespace std;
const int N = 1e4 + 10;
const int M = 1e5 + 10;
vector <int> g[N];
unordered_set <int> ap;
bool vs[N];
int disc[N], low[N];

void Setting();

int cnt = 0;
void tarjan(int u, int pre){
    vs[u] = true;
    cnt ++;
    disc[u] = cnt;
    low[u] = cnt;
    int child = 0;
    for(auto v: g[u]){
        if(!vs[v]){
            child ++;
            tarjan(v, u);
            low[u] = min(low[u], low[v]);
            if((pre != 0 and low[v] >= disc[u]) or (pre == 0 and child > 1))
                ap.insert(u);
        }
        else if(v != pre){
            low[u] = min(low[u], disc[v]);
        }
    }
}

void Solve(int n, int m){
    for(int i=1;i<=m;i++){
        int u, v;
        scanf("%d %d", &u, &v);
        g[u].push_back(v);
        g[v].push_back(u);
    }
    tarjan(1, 0);
    printf("%d", ap.size());
    Setting();
}

int main(){

    while(true){
        int n, m;
        scanf("%d %d", &n, &m);
        if(n == 0 and m == 0) return 0;
        Solve(n, m);
        printf("\n");
    }

    return 0;
}

void Setting(){
    for(int i=1;i<=N-10;i++){
        if(!g[i].empty()) g[i].clear();
    }
    if(!ap.empty()) ap.clear();
    for(int i=1;i<=N-10;i++){
        vs[i] = false;
        disc[i] = 0;
        low[i] = 0;
    }
}