Submission #246397

#	Time	Username	Problem	Language	Result	Execution time	Memory
246397		dantoh000	Pipes (CEOI15_pipes)	C++14	0 / 100	5076 ms	39236 KiB

pipes

#include <utility>
#include <vector>
#include <algorithm>
#include <cstdio>
using namespace std;
typedef pair<int,int> ii;
int n,m;
int d[100005], pa[100005], sz[100005];
int bad[100005];
vector<int> G[100005];
struct ufds{
    int p[100005];
    ufds(){
        for (int i = 0; i <= 100000; i++) p[i] = i;
    }
    int find(int x){
        return p[x] == x ? x : p[x] = find(p[x]);
    }
    void un(int x, int y){
        p[x] = y;
    }
} u1 = ufds(), u2 = ufds();
void dfs(int u, int p){
    pa[u] = p;
	for (auto v : G[u]){
		if (v == p) continue;
		else{
            d[v] = d[u]+1;
			pa[v] = u;
            dfs(v,u);
		}
	}
}

int main(){
    scanf("%d%d",&n,&m);
    for (int i = 0; i < m; i++){
        int u,v;
        scanf("%d%d",&u,&v);
        int pu = u1.find(u), pv = u1.find(v);
        //printf("%d -> %d, %d -> %d\n",u,pu,v,pv);
        if (pu == pv){
            printf("update path %d %d\n",u,v);
            ///make all edges along this path bad
            ///all edges along path are only changed once, O(N)
            u = u2.find(u), v = u2.find(v);
            while (u != v){
                if (d[u] < d[v]) swap(u,v);
                bad[u] = true;
                //printf("bad %d %d\n",u,pa[u]);
                u = pa[u];
                u = u2.find(u);
            }
        }
        else{
            //printf("join %d %d\n",u,v);
            ///join the two components
            if (sz[pu] < sz[pv]){
                swap(pu,pv);
                swap(u,v);
            }
            ///join small v to big u
            u1.un(pv,pu);
            sz[pu] += sz[pv];
            ///add edge
            G[u].push_back(v);
            G[v].push_back(u);
            ///restart dfs
            d[v] = d[u]+1;
            dfs(v,u);

        }
    }
    for (int i = 1 ; i<= n; i++){
        if (!bad[i] && pa[i] != 0){
            printf("%d %d\n",i,pa[i]);
        }
    }


}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:36:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d",&n,&m);
     ~~~~~^~~~~~~~~~~~~~
pipes.cpp:39:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d",&u,&v);
         ~~~~~^~~~~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 0 / 10
• Subtask 3: 0 / 10
• Subtask 4: 0 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10