[欧拉回路 并查集] Codeforces 547D #305 (Div. 1) D. Mike and Fish
2017-01-08 09:37
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这个题建图不难想 建成一个二分图 左边表示x右边表示y 然后在xy之间连边 奇点我们用一个额外点都连起来
然后就是找欧拉回路 用并查集 不然后T
#include<cstdio>
#include<cstdlib>
#include<algorithm>
using namespace std;
inline char nc(){
static char buf[100000],*p1=buf,*p2=buf;
if (p1==p2) { p2=(p1=buf)+fread(buf,1,100000,stdin); if (p1==p2) return EOF; }
return *p1++;
}
inline bool read(int &x){
char c=nc(),b=1;
for (;!(c>='0' && c<='9');c=nc()) if (c=='-') b=-1; else if (c==EOF) return 0;
for (x=0;c>='0' && c<='9';x=x*10+c-'0',c=nc()); x*=b; return 1;
}
const int N=200005;
int fat[N<<3];
inline void init(int n){
for (int i=1;i<=n;i++) fat[i]=i;
}
inline int Fat(int u){
return u==fat[u]?u:fat[u]=Fat(fat[u]);
}
struct edge{
int u,v,next;
}G[N<<3];
int head[N<<1],inum=1;
inline void add(int u,int v,int p){
G[p].u=u; G[p].v=v; G[p].next=head[u]; head[u]=p;
}
int vst[N<<3];
int icnt,sx
;
inline int Bin(int x){
return lower_bound(sx+1,sx+icnt+1,x)-sx;
}
int n,vis[N<<1];
int xs
,ys
;
int t1,t2;
int deg[N<<1];
#define V G[p].v
void dfs(int u){
vis[u]=1;
for (int p=Fat(head[u]);p;p=Fat(G[p].next)){
vst[p>>1]=(p&1)+1;
fat[p]=G[p].next;
fat[p^1]=G[p^1].next;
dfs(V);
}
}
int main(){
freopen("t.in","r",stdin);
freopen("t.out","w",stdout);
read(n); for (int i=1;i<=n;i++) read(xs[i]),read(ys[i]);
icnt=0;
for (int i=1;i<=n;i++) sx[++icnt]=xs[i];
sort(sx+1,sx+icnt+1); t1=icnt=unique(sx+1,sx+icnt+1)-sx-1;
for (int i=1;i<=n;i++) xs[i]=Bin(xs[i]);
icnt=0;
for (int i=1;i<=n;i++) sx[++icnt]=ys[i];
sort(sx+1,sx+icnt+1); t2=icnt=unique(sx+1,sx+icnt+1)-sx-1;
for (int i=1;i<=n;i++) ys[i]=Bin(ys[i]);
for (int i=1;i<=n;i++) add(xs[i],ys[i]+t1,++inum),add(ys[i]+t1,xs[i],++inum),deg[xs[i]]^=1,deg[t1+ys[i]]^=1;
for (int i=1;i<=t1+t2;i++) if (deg[i]) add(i,t1+t2+1,++inum),add(t1+t2+1,i,++inum);
init(inum);
for (int i=1;i<=t1+t2+1;i++)
if (!vis[i])
dfs(i);
for (int i=1;i<=n;i++)
putchar(vst[i]==1?'r':'b');
return 0;
}
然后就是找欧拉回路 用并查集 不然后T
#include<cstdio>
#include<cstdlib>
#include<algorithm>
using namespace std;
inline char nc(){
static char buf[100000],*p1=buf,*p2=buf;
if (p1==p2) { p2=(p1=buf)+fread(buf,1,100000,stdin); if (p1==p2) return EOF; }
return *p1++;
}
inline bool read(int &x){
char c=nc(),b=1;
for (;!(c>='0' && c<='9');c=nc()) if (c=='-') b=-1; else if (c==EOF) return 0;
for (x=0;c>='0' && c<='9';x=x*10+c-'0',c=nc()); x*=b; return 1;
}
const int N=200005;
int fat[N<<3];
inline void init(int n){
for (int i=1;i<=n;i++) fat[i]=i;
}
inline int Fat(int u){
return u==fat[u]?u:fat[u]=Fat(fat[u]);
}
struct edge{
int u,v,next;
}G[N<<3];
int head[N<<1],inum=1;
inline void add(int u,int v,int p){
G[p].u=u; G[p].v=v; G[p].next=head[u]; head[u]=p;
}
int vst[N<<3];
int icnt,sx
;
inline int Bin(int x){
return lower_bound(sx+1,sx+icnt+1,x)-sx;
}
int n,vis[N<<1];
int xs
,ys
;
int t1,t2;
int deg[N<<1];
#define V G[p].v
void dfs(int u){
vis[u]=1;
for (int p=Fat(head[u]);p;p=Fat(G[p].next)){
vst[p>>1]=(p&1)+1;
fat[p]=G[p].next;
fat[p^1]=G[p^1].next;
dfs(V);
}
}
int main(){
freopen("t.in","r",stdin);
freopen("t.out","w",stdout);
read(n); for (int i=1;i<=n;i++) read(xs[i]),read(ys[i]);
icnt=0;
for (int i=1;i<=n;i++) sx[++icnt]=xs[i];
sort(sx+1,sx+icnt+1); t1=icnt=unique(sx+1,sx+icnt+1)-sx-1;
for (int i=1;i<=n;i++) xs[i]=Bin(xs[i]);
icnt=0;
for (int i=1;i<=n;i++) sx[++icnt]=ys[i];
sort(sx+1,sx+icnt+1); t2=icnt=unique(sx+1,sx+icnt+1)-sx-1;
for (int i=1;i<=n;i++) ys[i]=Bin(ys[i]);
for (int i=1;i<=n;i++) add(xs[i],ys[i]+t1,++inum),add(ys[i]+t1,xs[i],++inum),deg[xs[i]]^=1,deg[t1+ys[i]]^=1;
for (int i=1;i<=t1+t2;i++) if (deg[i]) add(i,t1+t2+1,++inum),add(t1+t2+1,i,++inum);
init(inum);
for (int i=1;i<=t1+t2+1;i++)
if (!vis[i])
dfs(i);
for (int i=1;i<=n;i++)
putchar(vst[i]==1?'r':'b');
return 0;
}
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