SPOJ: Submerging Islands

#include <bits/stdc++.h>
using namespace std;

const int N = 1e4;

vector<vector<int>> adj;
int nVertex, nEdge, discCnt;

vector<bool> visited(0);
vector<int> low(0);
vector<int> disc(0);
set<int> art;
void DFS(int u, int p){
    visited[u] = true;
    low[u] = disc[u] = ++discCnt;
    int child = 0;
    for(int v : adj[u]){
        if(v == p){
            continue;
        }
        if(visited[v]){
            low[u] = min(low[u], disc[v]);
        } else {
            ++child;
            DFS(v, u);
            low[u] = min(low[u], low[v]);
            if((p == 0 && child > 1) || (p != 0 && low[v] >= disc[u])){
                art.insert(u);
            }
        }
    }
}

int main(){

    while(true){
        scanf("%d %d", &nVertex, &nEdge);
        if(nVertex == 0 && nEdge == 0){
            break;
        }
        adj.assign(nVertex + 1, vector<int>(0));
        visited.assign(nVertex + 1, false);
        low.assign(nVertex + 1, 0);
        disc.assign(nVertex + 1, 0);
        art.clear();
        discCnt = 0;
        for(int i = 1; i <= nEdge; ++i){
            int u, v;
            scanf("%d %d", &u, &v);
            adj[u].push_back(v);
            adj[v].push_back(u);
        }
        for(int i = 1; i <= nVertex; ++i){
            if(!visited[i]){
                DFS(i, 0);
            }
        }
        cout << art.size() << "\n";
    }

    return 0;
}