Submission #118764

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
118764	2019-06-19T16:48:17 Z	someone_aa	Highway Tolls (IOI18_highway)	C++17	6 / 100	204 ms	18812 KB

highway

#include "highway.h"
#include <bits/stdc++.h>
#define ll long long
#define pb push_back
#define mp make_pair
using namespace std;
const int maxn = 100100;
int n, m;
vector<int>w;
vector<int>gs[maxn];
vector<pair<int,int> > g[maxn];

vector<int>gt[maxn];

int dist[maxn][2], parent[maxn][2];
int pind[maxn];
bool visited[maxn];

ll dista;

map<pair<int,int>, int> ind;
int type[maxn];
vector<pair<int,int> > sta, stb;
bool important[maxn];

void bfs(int u, int v) {
    visited[u] = visited[v] = true;
    queue<pair<int,int> > q;

    type[u] = 0;
    type[v] = 1;
    q.push(mp(u, 0));
    q.push(mp(v, 1));

    pind[u] = pind[v] = -1;

    while(!q.empty()) {
        int curr = q.front().first;
        int currtype = q.front().second;
        q.pop();

        for(auto i:g[curr]) {
            int ni = i.first;
            int nind = i.second;
            if(visited[ni]) continue;
            visited[ni] = true;
            type[ni] = currtype;
            pind[ni] = nind;
            q.push(mp(ni, currtype));
        }
    }
}

int solve(int root, int d) {
    // build bfs tree
    memset(visited,false,sizeof(visited));
    //memset(parent,-1,sizeof(parent));

    vector<int>v, v2, vind;

    queue<int>q;
    q.push(root);

    visited[root] = true;
    parent[root][d] = -1;

    while(!q.empty()) {
        int curr = q.front();
        q.pop();

        v.pb(parent[curr][d]);
        v2.pb(curr);
        vind.pb(pind[curr]);

        if(pind[curr] != -1)
            important[pind[curr]] = true;

        for(auto i:gs[curr]) {
            if(!visited[i] && type[i] == type[curr]) {
                visited[i] = true;
                parent[i][d] = curr;
                dist[i][d] = dist[curr][d] + 1;
                q.push(i);
            }
        }
    }

    if(v.size() == 1) return v2[0];
    // perform binary search

    for(int i=0;i<v.size();i++) {
        if(v[i] == -1) continue; // root
        int cind = vind[i];
        w[cind] = 1;
    }

    for(int i=0;i<m;i++) {
        if(!important[i]) w[i] = 1;
    }

    int li = 0, ri = v.size() - 1;

    while(li < ri) {
        int mid = (li + ri) / 2;

        // all before mid put them as low cost and other as high cost
        for(int i=0;i<=mid;i++) {
            if(v[i] == -1) continue; // root
            int cind = vind[i];
            w[cind] = 0;
        }

        ll cdist = ask(w);
        for(int i=0;i<=mid;i++) {
            if(v[i] == -1) continue; // root
            int cind = vind[i];
            w[cind] = 1;
        }

        if(cdist == dista) {
            ri = mid;
        }
        else {
            li = mid + 1;
        }
    }

    for(int i=0;i<v.size();i++) {
        if(v[i] == -1) continue; // root
        int cind = vind[i];
        w[cind] = 0;
    }

    for(int i=0;i<m;i++) {
        if(!important[i]) w[i] = 0;
    }

    return v2[li];
}

void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
    n = N; m = U.size();
    int li=0, ri=m-1;

    for(int i=0;i<m;i++) {
        //ind[mp(U[i], V[i])] = ind[mp(V[i], U[i])] = i;
        gs[U[i]].pb(V[i]);
        gs[V[i]].pb(U[i]);

        g[U[i]].pb(mp(V[i], i));
        g[V[i]].pb(mp(U[i], i));

        w.pb(0);
    }

    dista = ask(w);
    while(li<ri) {
        int mid = (li+ri)/2;
        for(int i=li;i<=mid;i++) {
            w[i] = 1;
        }
        ll distb = ask(w);
        for(int i=li;i<=mid;i++) {
            w[i] = 0;
        }

        if(dista == distb) {
            li = mid + 1;
        }
        else {
            ri = mid;
        }
    }

    int x = li;
    int u = U[x], v = V[x];
    important[x] = true;

    //cout<<u<<" "<<v<<"\n";

    bfs(u, v);
    //preprocess();

    //memset(visited,false,sizeof(visited));
    //cout<<"Ans: "<<xx<<" "<<yy<<"\n";
    answer(solve(u, 0), solve(v, 1));
}

Compilation message

highway.cpp: In function 'int solve(int, int)':
highway.cpp:91:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<v.size();i++) {
                 ~^~~~~~~~~
highway.cpp:128:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<v.size();i++) {
                 ~^~~~~~~~~

Subtask #1
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Incorrect	8 ms	7392 KB	Output is incorrect: {s, t} is wrong.
2	Halted	0 ms	0 KB	-

Subtask #2
0 / 7.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	9 ms	7604 KB	Output is correct
2	Incorrect	26 ms	8860 KB	Output is incorrect: {s, t} is wrong.
3	Halted	0 ms	0 KB	-

Subtask #3
6.0 / 6.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	28 ms	8744 KB	Output is correct
2	Correct	43 ms	9840 KB	Output is correct
3	Correct	62 ms	11156 KB	Output is correct
4	Correct	175 ms	17912 KB	Output is correct
5	Correct	190 ms	17892 KB	Output is correct
6	Correct	177 ms	18432 KB	Output is correct
7	Correct	186 ms	18812 KB	Output is correct
8	Correct	204 ms	17692 KB	Output is correct
9	Correct	168 ms	18672 KB	Output is correct