Submission #1086244

#	Time	Username	Problem	Language	Result	Execution time	Memory
1086244		rayan_bd	Race (IOI11_race)	C++17	100 / 100	467 ms	53304 KiB

race

#include <bits/stdc++.h>

using namespace std;

#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")

const int mxNN = 2e5+1000;
const int mxN = 1e6 + 500;
const int INF = (int) 1e9;


vector<pair<int,int>> adj[mxNN];
int sz[mxNN],dp[mxN],K,ans=INF;
bool ok[mxNN];

void dfs(int node,int par){
    sz[node]=1;
    for(auto it:adj[node]){
        int adj=it.first;
        if(par!=adj&&!ok[adj]){
            dfs(adj,node);
            sz[node]+=sz[adj];
        }
    }
}

int find(int node,int par,int n){
    for(auto it:adj[node]){
        int adj=it.first;
        if(par!=adj&&!ok[adj]&&sz[it.first]*2>n){
            return find(it.first,node,n);
        }
    }
    return node;
}



void path_finder(int u,int par,int h,int tot){
    if(tot>K) return;
    ans=min(ans,dp[K-tot]+h);
    for(auto it:adj[u]){
        if(it.first!=par&&!ok[it.first]){
            if(tot+it.second>K) continue;
            path_finder(it.first,u,h+1,tot+it.second);
        }
    }
}

void path_optimize(int u,int par,int h,int tot,unordered_set<int> &st){
    if(tot>K) return;
    st.insert(tot);
    dp[tot]=min(dp[tot],h);
    for(auto it:adj[u]){
        if(it.first!=par&&!ok[it.first]){
            if(tot+it.second>K) continue;
            path_optimize(it.first,u,h+1,tot+it.second,st);
        }
    }
}

void decompose(int u){
    dfs(u,0);
    int cen=find(u,0,sz[u]);
    dp[0]=0;
    unordered_set<int> st;
    for(auto it:adj[cen]){
        if(!ok[it.first]){
            path_finder(it.first,cen,1,it.second);
            path_optimize(it.first,cen,1,it.second,st);
        }
    }
    for(auto it:st) dp[it]=INF;
    ok[cen]=1;
    for(auto it:adj[cen]){
        if(!ok[it.first]){
            decompose(it.first);
        }
    }
}

int best_path(int n,int k,int h[][2],int l[]){

    for(int i=0;i<n-1;++i){
        adj[h[i][0]].emplace_back(h[i][1],l[i]);
        adj[h[i][1]].emplace_back(h[i][0],l[i]);
    }
    memset(dp,0x3f,sizeof(dp));
    K=k;
    decompose(0);
    return ans>=INF?-1:ans;
}

Compilation message (stderr)

race.cpp:6: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    6 | #pragma GCC optimization ("O3")
      | 
race.cpp:7: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    7 | #pragma GCC optimization ("unroll-loops")
      |

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 22 / 22
• Subtask 4: 57 / 57