Submission #729095

#	Time	Username	Problem	Language	Result	Execution time	Memory
729095		grogu	Shortcut (IOI16_shortcut)	C++14	0 / 100	1 ms	340 KiB

shortcut

#include "shortcut.h"
#include <bits/stdc++.h>
#define endl '\n'
#define here cerr<<"=========================================\n"
#define dbg(x) cerr<<#x<<": "<<x<<endl;
#define ll long long
#define pb push_back
#define popb pop_back
#define all(a_) a_.begin(),a_.end()
#define pll pair<ll,ll>
#define sc second
#define fi first
#define llinf 1000000000000000LL
#define ceri(a,l,r) {cerr<<#a<<": ";for(ll i = l;i<=r;i++) cerr<<a[i]<< " ";cerr<<endl;}

using namespace std;
#define maxn 505
#define lg 9
ll n,c,tsz;
vector<pll> g[maxn];
vector<ll> cyc,ps,curr;
ll cyclen;
bool naso = 0;
bool inc[maxn];
bool vis[maxn];
ll len[maxn][maxn];
void dfs(ll u,ll par){
    vis[u] = 1;
    curr.pb(u);
    inc[u] = 1;
    for(pll p : g[u]){
        ll s = p.fi;
        ll w = p.sc;
        if(s==par) continue;

        if(inc[s]){
            while(curr.size()){
                cyc.pb(curr.back());
                curr.popb();
                if(cyc.back()==s) break;
            }
            for(ll x : curr) inc[x] = 0;
            naso = 1;
            return;
        }
        dfs(s,u);
        if(naso) return;
    }
    inc[u] = 0;
    curr.popb();
}
ll id[maxn];
ll in[maxn],out[maxn];
ll st[maxn][lg];
ll dept[maxn];
ll ti = 0;
void dfs2(ll u,ll par,ll poc){
    id[u] = poc;
    st[u][0] = par;
    in[u] = ++ti;
    for(pll p : g[u]){
        ll s = p.fi;
        ll w = p.sc;
        if(s==par) continue;
        dept[s] = dept[u] + w;
        dfs2(s,u,poc);
    }
    out[u] = ti-1;
}
bool intree(ll x,ll y){return in[y]<=in[x]&&out[y]>=out[x];}
ll lca(ll x,ll y){
    if(intree(x,y)) return y;
    if(intree(y,x)) return x;
    for(ll j = lg-1;j>=0;j--){
        if(!intree(x,st[y][j])) y = st[y][j];
    }
    return st[y][0];
}
ll dis[maxn];
void dfs3(ll u,ll par){
    for(pll p : g[u]){
        ll s = p.fi;
        ll w = len[u][s];
        if(s==par) continue;
        dis[s] = dis[u] + w;
        dfs3(s,u);
    }
}
ll naj(ll x){
    for(ll i = 1;i<=tsz;i++) dis[i] = llinf;
    dis[x] = 0;
    dfs3(x,x);
    ll ans = x;
    for(ll i = 1;i<=tsz;i++) if(dis[i]>dis[ans]) ans = i;
    return ans;
}
ll find_shortcut(int N, vector<int> L, vector<int> D, int C)
{
    n = N;
    tsz = n;
    c = C;
    for(ll i = 1;i<=2*n;i++) for(ll j = 1;j<=2*n;j++) len[i][j] = llinf;
    for(ll i = 1;i<n;i++){
        g[i].pb({i+1,L[i-1]});
        g[i+1].pb({i,L[i-1]});
        len[i][i+1] = len[i+1][i] = L[i-1];
    }
    for(ll i = 1;i<=n;i++) if(D[i-1]){
        g[i].pb({++tsz,D[i-1]});
        g[tsz].pb({i,D[i-1]});
        len[i][tsz] = len[tsz][i] = D[i-1];
    }
    ll ans = llinf;
    for(ll i = 1;i<=n;i++){
        for(ll j = i+2;j<=n;j++){
            g[i].pb({j,c});
            g[j].pb({i,c});
            len[i][j] = len[j][i] = c;
            for(ll k = 1;k<=tsz;k++) vis[k] = inc[k] = id[k] = in[k] = out[k] = dept[k] = 0;
            cyclen = 0;
            naso = 0;
            cyc.clear();
            curr.clear();
            dfs(1,1);
            ps.clear();
            ps.pb(0);
            for(ll k = 1;k<cyc.size();k++) ps.pb(ps[k-1] + len[cyc[k]][cyc[k-1]]);
            cyclen = ps.back() + len[cyc[0]][cyc.back()];
            for(ll k = 0;k<cyc.size();k++){
                ll y = cyc[k];
                st[y][0] = y;
                for(pll p : g[y]){
                    ll s = p.fi;
                    ll w = p.sc;
                    if(inc[s]) continue;
                    dept[s] = w;
                    dfs2(s,y,k);
                }
            }
            for(ll e = 1;e<lg;e++) for(ll k = 1;k<=tsz;k++) st[k][e] = st[st[k][e-1]][e-1];
            vector<ll> lif;
            for(ll k = 1;k<=tsz;k++) if(g[k].size()==1) lif.pb(k);
            ll cur = cyclen;
            for(ll e = 0;e<lif.size();e++){
                for(ll f = e+1;f<lif.size();f++){
                    ll x = lif[e],y = lif[f];
                    ll idx = id[x],idy = id[y];
                    if(idx<idy) swap(idx,idy);
                    ll r = ps[idx] - ps[idy];
                    if(idx==idy) cur = max(cur,dept[x]+dept[y]-2*dept[lca(x,y)]);
                    else cur = max(cur,dept[x] + dept[y] + min(cyclen-r,r));
                }
            }
            ans = min(ans,cur);
            len[i][j] = len[j][i] = llinf;
            g[i].popb();
            g[j].popb();
        }
    }
    for(ll i = 1;i<n;i++){
        len[i][i+1] = len[i+1][i] = min((ll)L[i-1],c);
        ll x = naj(1);
        ll y = naj(x);
        ans = min(ans,dis[y]);
        len[i][i+1] = len[i+1][i] = L[i-1];
    }
    return ans;
}
/**
4 10
10 20 20
0 40 0 30

9 30
10 10 10 10 10 10 10 10
20 0 30 0 0 40 0 40 0

3 3
1 1
1 1 1
**/

Compilation message (stderr)

shortcut.cpp: In function 'void dfs(long long int, long long int)':
shortcut.cpp:33:12: warning: unused variable 'w' [-Wunused-variable]
   33 |         ll w = p.sc;
      |            ^
shortcut.cpp: In function 'long long int find_shortcut(int, std::vector<int>, std::vector<int>, int)':
shortcut.cpp:119:62: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  119 |             for(ll k = 1;k<=tsz;k++) vis[k] = inc[k] = id[k] = in[k] = out[k] = dept[k] = 0;
      |                                                        ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
shortcut.cpp:127:27: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  127 |             for(ll k = 1;k<cyc.size();k++) ps.pb(ps[k-1] + len[cyc[k]][cyc[k-1]]);
      |                          ~^~~~~~~~~~~
shortcut.cpp:129:27: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  129 |             for(ll k = 0;k<cyc.size();k++){
      |                          ~^~~~~~~~~~~
shortcut.cpp:144:27: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  144 |             for(ll e = 0;e<lif.size();e++){
      |                          ~^~~~~~~~~~~
shortcut.cpp:145:33: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  145 |                 for(ll f = e+1;f<lif.size();f++){
      |                                ~^~~~~~~~~~~

• Subtask 1: 0 / 9
• Subtask 2: 0 / 14
• Subtask 3: 0 / 8
• Subtask 4: 0 / 7
• Subtask 5: 0 / 33
• Subtask 6: 0 / 22
• Subtask 7: 0 / 4
• Subtask 8: 0 / 3