Four school test push ice cubes

2<=n,m<=10^9,0<=k<=50000.

We find that useful lattices are not many, and after a detailed discussion of the classifications, only these squares are useful:

Four angles, as well as obstacles (or deceleration zone) itself and the upper and lower left and right four directions, as well as the obstacles in the row (and ±1) of the tail two.

Then we just have to sort all the obstacles and deceleration bands by X-Y and y-x, for each useful lattice two points to find left and right will push to where, even the end of the violent BFS can.

#include <iostream>#include<stdio.h>#include<math.h>#include<string.h>#include<time.h>#include<stdlib.h>#include<string>#include<bitset>#include<vector>#include<Set>#include<map>#include<queue>#include<algorithm>#include<sstream>#include<stack>#include<iomanip>using namespacestd;#definePB Push_back#defineMP Make_pairtypedef pair<int,int>Pii;typedefLong LongLl;typedefDoubleld;typedef Vector<int>VI;#defineFi first#defineSe Second#defineFe first#defineFO (x) {freopen (#x ".", "R", stdin), Freopen (#x ". Out", "w", stdout);}#defineEDG int m=0,fst[sz],vb[sz],nxt[sz];void ad_de (int a,int b) {++m;nxt[m]=fst[a];fst[a]=m;vb[m]=b;} void Adde (int a,int b) {Ad_de (A, b); Ad_de (b,a);}#defineEDGC int m=0,fst[sz],vb[sz],nxt[sz],vc[sz];void ad_de (int a,int b,int c) {++m;nxt[m]=fst[a];fst[a]=m;vb[m]=b;vc[m]=c;} void Adde (int a,int b,int c) {ad_de (a,b,c); Ad_de (b,a,c);}#defineES (x,e) (int e=fst[x];e;e=nxt[e])#defineVIZ {printf ("digraph g{\n"); for (int. i=1;i<=n;i++) for ES (i,e) printf ("%d->%d;\n", I,vb[e]); Puts ("}");#ifdef LOCAL#defineTIMER Cerr<<clock () << "ms\n"#else#defineTIMER#endif#defineSZ 1234567intn,m,k,n=0;intXs[sz],ys[sz],ts[sz];typedef pair<int,int>Pii;map&LT;PII,int>STA;BOOLCMP2 (PII a,pii b) {if(a.se!=b.se)returna.se<b.se; returna.fi<b.fi;} PII Ps[sz]; intpn=0;p II Ss[sz],rs[sz];intdx[4]={1,-1,0,0},dy[4]={0,0,-1,1};voidRecintAintb) {    if(Sta[pii (A, b)]==1)return; if(a<1|| b<1|| a>n| | B&GT;M)return; ps[++pn]=PII (A, b);}intLS (PII a) {returnLower_bound (ps+1, ps+1+PN,A)-PS;}ints,t;intQs[sz];intDist[sz];#undefSZ#defineSZ 1234567EDGvoidConn (PII A,pii b) {if(a==b)return; Ad_de (LS (a), LS (b));voidSPFA () {intH=0, t=0; Qs[t++]=s; dist[s]=1;  while(h^t) {intx=qs[h++];  fores (x,e) {intb=Vb[e]; if(Dist[b])Continue; DIST[B]=dist[x]+1; Qs[t++]=C; }    }}intMain () {FO (ICE) scanf ("%d%d%d",&n,&m,&k);  for(intI=1; i<=k;i++) {scanf ("%d%d%d", xs+i,ys+i,ts+i); Sta[pii (Xs[i],ys[i])=ts[i]+1; } rec (1,1);    Rec (N,M); Rec (1, m); Rec (n,1);  for(intI=1; i<=k;i++) {rec (xs[i],1);        Rec (XS[I],M); Rec (1, Ys[i]);        Rec (n,ys[i]); Rec (Xs[i]+1,1); Rec (xs[i]+1, M); Rec (Xs[i]-1,1); Rec (xs[i]-1, M); Rec (1, ys[i]+1); Rec (n,ys[i]+1); Rec (1, ys[i]-1); Rec (n,ys[i]-1);        Rec (xs[i],ys[i]);  for(intj=0;j<4; j + +) Rec (xs[i]+dx[j],ys[i]+Dy[j]); } sort (ps+1, ps+1+PN); PN=unique (ps+1, ps+1+PN)-ps-1; intsn=0, rn=0;  for(intI=1; i<=k;i++)    {        if(ts[i]==0) ss[++sn]=PII (Xs[i],ys[i]); Elsers[++rn]=PII (Xs[i],ys[i]); } ss[++SN]=PII (-2000000000,-2000000000); ss[++SN]=PII (2000000000,2000000000); rs[++RN]=PII (-2000000000,-2000000000); rs[++RN]=PII (2000000000,2000000000); Sort (ss+1, ss+1+SN); Sort (rs+1, rs+1+RN); //handle the left and right first     for(intI=1; i<=pn;i++)    {        intx=ps[i].fi,y=ps[i].se; PII cur=PII (x, y); if(y!=1)//L        {        intmaxn=1; intId=lower_bound (rs+1, rs+1+rn,cur)-rs-1; PII NS=Rs[id]; if(ns.fi==x) maxn=Max (maxn,ns.se); ID=lower_bound (ss+1, ss+1+sn,cur)-ss-1; NS=Ss[id]; if(ns.fi==x) Maxn=max (maxn,ns.se+1);        Conn (Cur,pii (X,MAXN)); }        if(y!=m)//R        {        intminn=m; intId=upper_bound (rs+1, rs+1+rn,cur)-rs; PII NS=Rs[id]; if(ns.fi==x) minn=min (minn,ns.se); ID=upper_bound (ss+1, ss+1+sn,cur)-SS; NS=Ss[id]; if(ns.fi==x) Minn=min (minn,ns.se-1);        Conn (Cur,pii (X,minn)); }} sort (ss+1, ss+1+SN,CMP2); Sort (rs+1, rs+1+RN,CMP2);  for(intI=1; i<=pn;i++)    {        intx=ps[i].fi,y=ps[i].se; PII cur=PII (x, y); if(x!=1)//U        {        intmaxn=1; intId=lower_bound (rs+1, rs+1+RN,CUR,CMP2)-rs-1; PII NS=Rs[id]; if(ns.se==y) maxn=Max (maxn,ns.fi); ID=lower_bound (ss+1, ss+1+SN,CUR,CMP2)-ss-1; NS=Ss[id]; if(ns.se==y) Maxn=max (maxn,ns.fi+1);        Conn (Cur,pii (maxn,y)); }        if(x!=n)//R        {        intminn=N; intId=upper_bound (rs+1, rs+1+RN,CUR,CMP2)-rs; PII NS=Rs[id]; if(ns.se==y) minn=min (minn,ns.fi); ID=upper_bound (ss+1, ss+1+SN,CUR,CMP2)-SS; NS=Ss[id]; if(ns.se==y) Minn=min (minn,ns.fi-1);        Conn (Cur,pii (minn,y)); }} S=ls (PII (1,1)); t=ls (PII (n,m)); SPFA (); cout<<dist[t]-1<<"\ n";}

Four school test push ice cubes