bzoj3362[Usaco2004 Feb]Navigation Nightmare 导航噩梦(带权并查集)
2017-09-05 16:25
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把询问离线了,按时间顺序排序,做好询问时间以前的。用带权并查集维护,因为要求曼哈顿距离,所以我们记录dx[i]数组表示x[fa[i]]-x[i],注意是有方向的。dy[i]同理。合并时处理好方向问题。还是那句话,画向量图来帮助你思维。
有没有哪位神犇能告诉我usaco green是个什么分级么。。跟gold pt不一样?
有没有哪位神犇能告诉我usaco green是个什么分级么。。跟gold pt不一样?
#include <cstdio> #include <cstring> #include <algorithm> #define N 40010 inline int read(){ int x=0,f=1;char ch=getchar(); while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();} while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar(); return x*f; } int n,m,k,fa ,dx ,dy ,ans[10010];//dx[i]--x[fa[i]]-x[i] struct edge{ int x,y,val;char op[1]; }a ; struct query{ int x,y,tim,id; }q[10010]; inline bool cmp(query x,query y){return x.tim<y.tim;} inline int find(int x){ if(fa[x]==x) return x; int xx=find(fa[x]); dx[x]+=dx[fa[x]];dy[x]+=dy[fa[x]]; return fa[x]=xx; } int main(){ // freopen("a.in","r",stdin); n=read();m=read(); for(int i=1;i<=n;++i) fa[i]=i; for(int i=1;i<=m;++i){ 11949 a[i].x=read(),a[i].y=read(),a[i].val=read();scanf("%s",a[i].op); }k=read(); for(int i=1;i<=k;++i) q[i].x=read(),q[i].y=read(),q[i].tim=read(),q[i].id=i; std::sort(q+1,q+k+1,cmp);int now=1; for(int i=1;i<=k;++i){ while(now<=q[i].tim){ int x=a[now].x,y=a[now].y; int xx=find(x),yy=find(y); if(xx==yy) continue;fa[xx]=yy; dx[xx]=dx[y]-dx[x];dy[xx]=dy[y]-dy[x]; if(a[now].op[0]=='E') dx[xx]+=a[now].val; if(a[now].op[0]=='W') dx[xx]-=a[now].val; if(a[now].op[0]=='N') dy[xx]+=a[now].val; if(a[now].op[0]=='S') dy[xx]-=a[now].val;now++; } int x=q[i].x,y=q[i].y; int xx=find(x),yy=find(y); if(xx==yy) ans[q[i].id]=abs(dx[x]-dx[y])+abs(dy[x]-dy[y]); else ans[q[i].id]=-1; } for(int i=1;i<=k;++i) printf("%d\n",ans[i]); return 0; }
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