Submission #386966

#	Time	Username	Problem	Language	Result	Execution time	Memory
386966		jeroenodb	Bitaro’s Party (JOI18_bitaro)	C++14	100 / 100	760 ms	85356 KiB

bitaro

#pragma GCC optimize("Ofast")
#pragma GCC target("avx")
#include "bits/stdc++.h"
using namespace std;
#define all(x) begin(x),end(x)
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { string sep; for (const T &x : v) os << sep << x, sep = " "; return os; }
#define debug(a) cerr << "(" << #a << ": " << a << ")\n";
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pi;
const int mxN = 1e5+1, oo = 1e9;
const int K = 100;
int n;
vi adj[mxN];
pi dp[mxN][K];
int sz[mxN];
pi merger[2*K];
int input[mxN];
bitset<mxN> banned;
int longest[mxN];
pi* mymerge(pi* p1, pi* e1, pi* p2, pi* e2) {
    pi* a= merger;
    while(p1!=e1 and p2!=e2 and a-merger<K) {
        if(banned[p1->second]) p1++;
        else if(banned[p2->second]) p2++;
        else if(*p1 > *p2) {
            banned[p1->second]=true;
            *(a++) = *(p1++);
        } else {
            banned[p2->second]=true;
            *(a++) = *(p2++);
        }

    }
    
    while(p1!=e1) {
        *a = *p1;
        if(!banned[p1++->second]) 
            a++;
    } 
    while(p2!=e2) {
        *a = *p2;
        if(!banned[p2++->second]) 
            a++;
    }
    for(pi* i =merger;i!=a;++i) banned[i->second] = false;
    return a;
}
void precomp() {
    // find best K for every party position
    for(int i=0;i<n;++i) {
        dp[i][0] = {-1,i};
        sz[i] = 1;
        for(int to: adj[i]) {
            auto iter = mymerge(dp[i],dp[i]+sz[i], dp[to],dp[to]+sz[to]);
            // wrong, because answer may be more than one time in the dp array, more difficult merge is needed
            sz[i] = min(K,(int)(iter-merger));
            copy(merger,merger + sz[i], dp[i]); 
        }
        for(int j=0;j<sz[i];++j) dp[i][j].first++;
    }
    
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int m,q; cin >> n >> m >> q;
    while(m--) {
        int a,b; cin >> a >> b; --a,--b;
        adj[b].push_back(a);
    }
    precomp();
    while(q--) {
        int party, y; cin >> party >> y; party--;
        for(int i=0;i<y;++i) {
            cin >> input[i]; input[i]--; 
            banned[input[i]] =true;
        }

        if(y<K) {
            // Have stored the answer already in DP, just pick it out

            int ans = -1;
            for(int i=0;i<sz[party];++i) {
                auto [length,to] = dp[party][i];
                if(!banned[to]) {
                    ans = length;
                    break;
                }
            }
            cout << ans << '\n';

        } else {
            // Do the calculation of longest paths all over. O(M) worstcase, but only happens n/k times
            for(int i=0;i<=party;++i) {
                if(banned[i]) 
                    longest[i] = -oo;
                else longest[i] = 0;
                for(int to: adj[i]) {
                    longest[i] = max(longest[i],longest[to]+1);
                }
            }
            cout << (longest[party]<0?-1:longest[party]) << '\n';
        }
        for(int i=0;i<y;++i) banned[input[i]]=false;
    }
}

Compilation message (stderr)

bitaro.cpp: In function 'int main()':
bitaro.cpp:87:22: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   87 |                 auto [length,to] = dp[party][i];
      |                      ^

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 86 / 86