Submission #50139

#	Time	Username	Problem	Language	Result	Execution time	Memory
50139		top34051	Parachute rings (IOI12_rings)	C++17	100 / 100	826 ms	51584 KiB

rings

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

const int maxn = 1e6 + 5;

int n, m, ok;
pair<int,int> e[maxn];

int cyc, cysz, head0[maxn], deg0[maxn], sz0[maxn];

int ban[5], bad[5], head[5][maxn], deg[5][maxn];

void Init(int _n) {
    n = _n;
    for(int i=1;i<=n;++i) head0[i] = i, sz0[i] = 1;
    for(int k=1;k<=4;++k) {
        for(int i=1;i<=n;++i) head[k][i] = i;
    }
}

int CountCritical() {
    if(!ok) {
        if(cyc==0) return n;
        if(cyc==1) return cysz;
        return 0;
    }
    else {
        int res = 0;
        for(int i=1;i<=4;i++) res += !bad[i];
        return res;
    }
}

int findhead(int k, int x) {
    if(head[k][x]==x) return x;
    return head[k][x] = findhead(k, head[k][x]);
}

int findhead0(int x) {
    if(head0[x]==x) return x;
    return head0[x] = findhead0(head0[x]);
}

void edge(int k, int u, int v) {
    if(ban[k]==u || ban[k]==v) return ;

    ++deg[k][u]; ++deg[k][v];
    if(deg[k][u]==3) bad[k] = 1;
    if(deg[k][v]==3) bad[k] = 1;

    int x = findhead(k,u), y = findhead(k,v);
    if(x==y) bad[k] = 1;
    else head[k][x] = y;
}

void edge0(int u, int v) {
    if(cyc>1) return ;

    ++deg0[u]; ++deg0[v];

    int x = findhead0(u), y = findhead0(v);
    if(x==y) {
        ++cyc;
        cysz = sz0[x];
    }
    else {
        sz0[y] += sz0[x];
        head0[x] = y;
    }
}

void build(int x) {
    ok = 1;
    int cur = 0;
    ban[++cur] = x;
    for(int i=1;i<=m;++i) {
        if(e[i].first==x) ban[++cur] = e[i].second;
        if(e[i].second==x) ban[++cur] = e[i].first;
    }
    for(int k=1;k<=4;++k) {
        for(int i=1;i<=m;++i) {
            if(bad[k]) break;
            edge(k,e[i].first,e[i].second);
        }
    }
}

void Link(int x, int y) {
    ++x; ++y;
    e[++m] = {x,y};

    if(!ok) {
        edge0(x,y);
        if(deg0[x]==3) build(x);
        else if(deg0[y]==3) build(y);
    }
    else {
        for(int k=1;k<=4;++k) if(!bad[k]) edge(k,x,y);
    }
}

• Subtask 1: 20 / 20
• Subtask 2: 17 / 17
• Subtask 3: 18 / 18
• Subtask 4: 14 / 14
• Subtask 5: 31 / 31