Submission #874340

#	Time	Username	Problem	Language	Result	Execution time	Memory
874340		Matjaz	Jousting tournament (IOI12_tournament)	C++14	100 / 100	68 ms	5576 KiB

tournament

#include <vector>
#include <algorithm>
#include <iostream>

using namespace std;


// Insight: each S[i] E[i] corresponds to some interval in the original set of positions
// The interval only matters if your player is in it - and there is a unique answer as to whether it wins or loses
// You can find the best position with a sweep.
// Does linked list + fenwick tree work?

vector<int> tree;
int N;

int sum(int x){
    int s = 0;
    x++;
    while (x > 0){
        s += tree[x];
        x -= x & (-x);
    }
    
    return s;
}

int find(int x){
    
    int l = 0;
    int u = N - 1;
    
    while (l < u){
        int mid = l + (u - l) / 2;
        //cout << mid << " " << sum(mid) << endl;
        if (sum(mid) < x) l = mid + 1; else u = mid;
    }
    
    return l;
}

void update(int x,int v){
    x++;
    while (x <= tree.size()){
        tree[x] += v;
        x += x & (-x);
    }
}


int GetBestPosition(int _N, int C, int R, int *K, int *S, int *E) {
    N = _N;
    vector<int> s(N+1);
    s[0] = 0;
    for (int i=1;i<=N;i++) s[i] = s[i-1] + (K[i-1] > R);
    
    vector<int> next(N);
    for (int i=0;i<N;i++) next[i] = i + 1;
    
    vector<pair<int,int> > sweep_events;
    tree.assign(N + 2, 0);
    for (int i=0;i<N;i++) update(i, 1);
    
    
    for (int i=0;i<C;i++){
        
        int left = find(S[i] + 1);
        int right = find(E[i] + 1);
        
        //We can put in assert(left is active)
        
        int tmp = left;
        while (tmp != right){
            tmp = next[tmp];
            update(tmp, -1);
        }
        next[left] = next[right];
        
        right = next[left] - 1;
        
        //cout << S[i] << " " << E[i] << " " << left << " " << right << endl;
    
        if (s[right] - s[left] == 0){
            sweep_events.push_back(make_pair(left, 1));
            sweep_events.push_back(make_pair(right + 1, -1));
        }
        
    }
    
    sort(sweep_events.begin(), sweep_events.end());
    
    int best_position = 0;
    int best_wins = 0;
    int wins = 0;

    
    for (int i=0;i<sweep_events.size();i++){
        wins += sweep_events[i].second;
        if (wins > best_wins){
            best_wins = wins;
            best_position = sweep_events[i].first;
        }
    }
    
    
    return best_position;
}

Compilation message (stderr)

tournament.cpp: In function 'void update(int, int)':
tournament.cpp:43:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   43 |     while (x <= tree.size()){
      |            ~~^~~~~~~~~~~~~~
tournament.cpp: In function 'int GetBestPosition(int, int, int, int*, int*, int*)':
tournament.cpp:96:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   96 |     for (int i=0;i<sweep_events.size();i++){
      |                  ~^~~~~~~~~~~~~~~~~~~~

• Subtask 1: 17 / 17
• Subtask 2: 32 / 32
• Subtask 3: 51 / 51