Submission #16415

#	Time	Username	Problem	Language	Result	Execution time	Memory
16415		comet	경주 (Race) (IOI11_race)	C++98	0 / 100	5 ms	4360 KiB

race

#include<cstdio>
#include<algorithm>
#include<vector>
#include<queue>
#include<cstring>
#define pb push_back
using namespace std;
struct edge{
	int u,c;
};
struct state{
	int v,c,len;
};
typedef long long ll;
typedef vector<int> vec;
typedef vector<edge> Evec;

vector<Evec> path;

int N,K;
int a[1000010];
int SubSz[200000],MaxSz[200000];
bool cover[200000],chk[200000];

int dfs(int v){
	chk[v]=1;
	SubSz[v]=MaxSz[v]=1;
	for(int i=0;i<path[v].size();i++){
		int u=path[v][i].u;
		if(!chk[u]&&!cover[u]){
			int t=dfs(u);
			SubSz[v]+=t;
			MaxSz[v]=max(MaxSz[v],t+1);
		}
	}
	return SubSz[v];
}

int centroid(int root,int cnt){
	dfs(root);
	int Min=1e9,ret;
	for(int i=0;i<N;i++){
		if(chk[i]&&!cover[i]){
			if(Min>max(MaxSz[i],cnt-MaxSz[i])){
				Min=max(MaxSz[i],cnt-MaxSz[i]);
				ret=i;
			}
			chk[i]=0;
		}
	}
	return ret;
}

int f(int root,int cnt){
	if(cnt==1)return 1e9;
	root=centroid(root,cnt);
	cover[root]=1;

	int ret=1e9;
	/*printf("root : %d\n",root);
	for(int i=0;i<N;i++)printf("%d ",cover[i]);puts("");
	for(int i=0;i<N;i++)printf("%d ",chk[i]);puts("");*/

	for(int i=0;i<path[root].size();i++){
		int nxt=path[root][i].u;
		int cost=path[root][i].c;
		if(cover[nxt])continue;
		ret=min(ret,f(nxt,SubSz[nxt]));
		//printf("%d-->%d : %d\n",root,nxt,ret);
	}


	for(int i=0;i<path[root].size();i++){
		int nxt=path[root][i].u;
		int cost=path[root][i].c;
		if(cover[nxt])continue;

		queue<state> Q;
		Q.push(state{nxt,cost,1});

		while(!Q.empty()){
			state h=Q.front();
			Q.pop();
			if(h.c>K)continue;
			ret=min(ret,a[K-h.c]+h.len);
			for(int j=0;j<path[h.v].size();j++){
				int u=path[h.v][j].u;
				if(!cover[u]&&!chk[u]){
					chk[u]=1;
					Q.push(state{u,h.c+path[h.v][j].c,h.len+1});
				}
			}
		}
		Q.push(state{nxt,cost,1});
		while(!Q.empty()){
			state h=Q.front();
			Q.pop();
			if(h.c>K)continue;
			if(h.c==K)ret=min(ret,h.len);
			a[h.c]=min(a[h.c],h.len);
			for(int j=0;j<path[h.v].size();j++){
				int u=path[h.v][j].u;
				if(!cover[u]&&chk[u]){
					chk[u]=0;
					Q.push(state{u,h.c+path[h.v][j].c,h.len+1});
				}
			}
		}
	}

	for(int i=0;i<path[root].size();i++){
		int nxt=path[root][i].u;
		int cost=path[root][i].c;
		if(cover[nxt])continue;

		queue<state> Q;
		Q.push(state{nxt,cost,1});
		while(!Q.empty()){
			state h=Q.front();
			Q.pop();
			if(h.c>K)continue;
			for(int j=0;j<path[h.v].size();j++){
				int u=path[h.v][j].u;
				if(!cover[u]&&!chk[u]){
					chk[u]=1;
					Q.push(state{u,h.c+path[h.v][j].c,h.len+1});
				}
			}
		}
		Q.push(state{nxt,cost,1});
		while(!Q.empty()){
			state h=Q.front();
			Q.pop();
			if(h.c>K)continue;
			a[h.c]=1e9;
			for(int j=0;j<path[h.v].size();j++){
				int u=path[h.v][j].u;
				if(!cover[u]&&chk[u]){
					chk[u]=0;
					Q.push(state{u,h.c+path[h.v][j].c,h.len+1});
				}
			}
		}
	}
	cover[root]=0;
	return ret;
}

int best_path(int N_,int K_,int H[][2],int L[]){
	N=N_,K=K_;
	memset(a,0x3f,sizeof(a));
	path.assign(N,Evec());
	for(int i=0;i<N-1;i++){
		path[H[i][0]].pb(edge{H[i][1],L[i]});
		path[H[i][1]].pb(edge{H[i][0],L[i]});
	}
	int ret=f(0,N);
	if(ret>N)return -1;
	return ret;
}

Compilation message (stderr)

race.cpp: In function 'int dfs(int)':
race.cpp:28:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<path[v].size();i++){
              ~^~~~~~~~~~~~~~~
race.cpp: In function 'int f(int, int)':
race.cpp:64:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<path[root].size();i++){
              ~^~~~~~~~~~~~~~~~~~
race.cpp:66:7: warning: unused variable 'cost' [-Wunused-variable]
   int cost=path[root][i].c;
       ^~~~
race.cpp:73:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<path[root].size();i++){
              ~^~~~~~~~~~~~~~~~~~
race.cpp:86:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int j=0;j<path[h.v].size();j++){
                ~^~~~~~~~~~~~~~~~~
race.cpp:101:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int j=0;j<path[h.v].size();j++){
                ~^~~~~~~~~~~~~~~~~
race.cpp:111:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<path[root].size();i++){
              ~^~~~~~~~~~~~~~~~~~
race.cpp:122:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int j=0;j<path[h.v].size();j++){
                ~^~~~~~~~~~~~~~~~~
race.cpp:136:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int j=0;j<path[h.v].size();j++){
                ~^~~~~~~~~~~~~~~~~
race.cpp: In function 'int centroid(int, int)':
race.cpp:51:9: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return ret;
         ^~~

• Subtask 1: 0 / 9
• Subtask 2: 0 / 12
• Subtask 3: 0 / 22
• Subtask 4: 0 / 57