Submission #246261

#	Time	Username	Problem	Language	Result	Execution time	Memory
246261		dantoh000	Pipes (CEOI15_pipes)	C++14	20 / 100	2567 ms	65540 KiB

pipes

#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> ii;
const int N = 100005;
int n,m;
ii edg[6000006];
vector<ii> bad;
vector<int> G[N];
int p[N], d[N], sz[N], h[N], pos[N], S[N];
int ct = 0;
int badct = 0;
void dfs(int u){
	sz[u] = 1;
	for (auto v : G[u]){
		if (p[v] == 0){
			p[v] = u;
			d[v] = d[u]+1;
			dfs(v);
			sz[u] += sz[v];
		}
	}
}

void decomp(int u){
	pos[u] = ct++;
	//printf("%d %d\n",u,ct);
	int heavy = 0;
	for (auto v : G[u]){
		if (p[v] != u) continue;
		if (sz[heavy] < sz[v]) heavy = v;
	}
	if (heavy == 0) return;
	h[heavy] = h[u];
	decomp(heavy);
	for (auto v : G[u]){
        if (p[v] != u) continue;
		if (v != heavy && v != p[u]) decomp(v);
	}
}

void up(int u, int v){
	while (h[u] != h[v]){
		if (u == -1 || v == -1) return;
		if (d[h[u]] > d[h[v]]) swap(u,v);
		//printf("updating %d to %d\n",v,h[v]);
		S[pos[h[v]]]++;
		S[pos[v]+1]--;
		v = p[h[v]];
	}
	if (d[u] > d[v]) swap(u,v);
	S[pos[u]+1]++;
    S[pos[v]+1]--;
}

int main(){
    scanf("%d%d",&n,&m);

    for (int i = 0; i < m; i++){
        int u,v;
        scanf("%d%d",&u,&v);
        edg[i] = ii(u,v);
    }
    sort(edg,edg+m);
    for (int i = 0; i < m; i++){
        if (i == m-1 || (edg[i].first != edg[i+1].first || edg[i].second != edg[i+1].second)){
            int u,v;
            tie(u,v) = edg[i];
            int Bad = (i && (u == edg[i-1].first && v == edg[i-1].second));
            if (!Bad) edg[i] = ii(-1,-1);
            G[u].push_back(v);
            G[v].push_back(u);
        }
    }
    iota(h,h+N,0);
    for (int i = 1; i <= n; i++){
        if (p[i] == 0){
            p[i] = -1;
            dfs(i);
            decomp(i);
        }
    }
    for (int u = 1; u <= n; u++){
        sort(G[u].begin(),G[u].end());
        for (auto v : G[u]){
            if (p[v] != u && p[u] != v) up(u,v);
        }
    }
    for (int i = 0; i < m; i++){
        if (edg[i] != ii(-1,-1)) up(edg[i].first,edg[i].second);
    }
    for (int i = 1; i <= n+1; i++){
        S[i] += S[i-1];
    }
    for (int i = 1; i <= n; i++){
        //printf("edge<%d %d> = %d\n",i,p[i],S[pos[i]]);
        if (S[pos[i]] == 0 && p[i] != -1){
            printf("%d %d\n",p[i],i);
        }
    }

}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:56:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d",&n,&m);
     ~~~~~^~~~~~~~~~~~~~
pipes.cpp:60:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d",&u,&v);
         ~~~~~^~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 0 / 10
• Subtask 4: 0 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10