Submission #121245

#	Time	Username	Problem	Language	Result	Execution time	Memory
121245		Plurm	Flood (IOI07_flood)	C++11	26 / 100	183 ms	12520 KiB

flood

#include <bits/stdc++.h>
#define get(a,b) (ev[g[a][b]].first ^ ev[g[a][b]].second ^ a)
using namespace std;
int x[100005];
int y[100005];
int g[100005][4]; // U, L, D, R
class Compare{
public:
    bool operator()(int x, int y){
        return ::x[x] < ::x[y];
    }
};
int prior[4][4] = {
        {1, 0, 3, 2}, // U
        {2, 1, 0, 3}, // L
        {3, 2, 1, 0}, // D
        {0, 3, 2, 1}
};
int inv[4] = {2, 3, 0, 1};
bool deleted[200005];
vector<pair<int,int> > ev;
void deleteEdge(int idx){
    int u = ev[idx].first;
    int v = ev[idx].second;
    for(int i = 0; i < 4; i++){
        int j = inv[i];
        if(get(u,i) == v && get(v,j) == u){
            g[u][i] = -1;
            g[v][j] = -1;
        }
    }
}
int main(){
    memset(g, -1, sizeof(g));
    int n;
    scanf("%d",&n);
    multiset<int, Compare> ms;
    for(int i = 1; i <= n; i++){
        scanf("%d%d",x+i,y+i);
    }
    for(int i = 1; i <= n; i++){
        ms.insert(i);
    }
    int w;
    scanf("%d",&w);
    for(int i = 0; i < w; i++){
        int a,b;
        scanf("%d%d",&a,&b);
        if(x[a] > x[b]) swap(a,b);
        if(y[a] > y[b]) swap(a,b);
        if(x[a] < x[b]){
            g[a][3] = i;
            g[b][1] = i;
        }else{
            g[a][0] = i;
            g[b][2] = i;
        }
        ev.push_back(make_pair(a,b));
    }
    while(!ms.empty()){
        int c = *ms.begin();
        int state = 0;
        // 0: Going up
        // 1: Going left
        // 2: Going down
        // 3: Going right
        int u = c;
        vector<int> tour;
        vector<int> edge;
        map<int,int> ecnt;
        // U L D R
        do{
            // Trace the border
            tour.push_back(u);
            for(int i = 0; i < 4; i++){
                int chdir = prior[state][i];
                if(g[u][chdir] != -1){
                    state = chdir;
                    ecnt[g[u][chdir]]++;
                    edge.push_back(g[u][chdir]);
                    u = get(u,chdir);
                    break;
                }
            }
        }while(u != c);
        for(int i = 0; i < edge.size(); i++){
            int en = edge[i];
            deleteEdge(en);
            if(ecnt[en] % 2 == 0) continue;
            deleted[en] = true;
        }
        for(int i = 0; i < tour.size(); i++){
            int cnt = 0;
            for(int j = 0; j < 4; j++) if(g[tour[i]][j] != -1) cnt++;
            if(cnt == 0) ms.erase(tour[i]);
        }
    }
    vector<int> ans;
    for(int i = 0; i < w; i++){
        if(!deleted[i]){
            ans.push_back(i+1);
        }
    }
    printf("%d\n",ans.size());
    for(int i = 0; i < ans.size(); i++){
        printf("%d\n",ans[i]);
    }
    return 0;
}
/*
15
1 1
8 1
4 2
7 2
2 3
4 3
6 3
2 5
4 5
6 5
4 6
7 6
1 8
4 8
8 8
17
1 2
2 15
15 14
14 13
13 1
14 11
11 12
12 4
4 3
3 6
6 5
5 8
8 9
9 11
9 10
10 7
7 6
 */

Compilation message (stderr)

flood.cpp: In function 'int main()':
flood.cpp:86:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = 0; i < edge.size(); i++){
                        ~~^~~~~~~~~~~~~
flood.cpp:92:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = 0; i < tour.size(); i++){
                        ~~^~~~~~~~~~~~~
flood.cpp:104:29: warning: format '%d' expects argument of type 'int', but argument 2 has type 'std::vector<int>::size_type {aka long unsigned int}' [-Wformat=]
     printf("%d\n",ans.size());
                   ~~~~~~~~~~^
flood.cpp:105:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0; i < ans.size(); i++){
                    ~~^~~~~~~~~~~~
flood.cpp:36:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
     ~~~~~^~~~~~~~~
flood.cpp:39:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d",x+i,y+i);
         ~~~~~^~~~~~~~~~~~~~~~
flood.cpp:45:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&w);
     ~~~~~^~~~~~~~~
flood.cpp:48:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d",&a,&b);
         ~~~~~^~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 0 / 10
• Subtask 3: 10 / 10
• Subtask 4: 0 / 3
• Subtask 5: 0 / 10
• Subtask 6: 3 / 3
• Subtask 7: 3 / 3
• Subtask 8: 0 / 3
• Subtask 9: 0 / 3
• Subtask 10: 0 / 9
• Subtask 11: 0 / 9
• Subtask 12: 0 / 9
• Subtask 13: 0 / 9
• Subtask 14: 0 / 9