bzoj1594

首先想到二分答案

然后我们从大往小加区间，如果之前出现了一个区间包含当前区间

那显然不合法，我们可以用并查集了维护

 type node=record
        x,y,mi,id:longint;
      end;

 var q:array[..] of node;
     a:array[..] of longint;
     fa:array[..] of longint;
     l,r,m,n,t,i,ans:longint;

 function min(a,b:longint):longint;
   begin
     if a>b then exit(b) else exit(a);
   end;

 function max(a,b:longint):longint;
   begin
     if a>b then exit(a) else exit(b);
   end;

 procedure swap(var a,b:node);
   var c:node;
   begin
     c:=a;
     a:=b;
     b:=c;
   end;

 procedure sort(l,r:longint);
   var i,j,x:longint;
   begin
     i:=l;
     j:=r;
     x:=q[(l+r) shr ].mi;
     repeat
       while x<q[i].mi do inc(i);
       while q[j].mi<x do dec(j);
       if not(i>j) then
       begin
         swap(q[i],q[j]);
         inc(i);
         dec(j);
       end;
     until i>j;
     if l<j then sort(l,j);
     if i<r then sort(i,r);
   end;

 function have(l,r:longint):boolean;
   var x:longint;
   begin
     x:=r;
     while x>=l do
     begin
       if fa[x]= then exit(false);
       x:=fa[x]-;
     end;
     exit(true);
   end;

 procedure work(l,r:longint);
   var x:longint;
   begin
     x:=r;
     while x>=l do
     begin
       if fa[x]= then fa[x]:=l
       else begin
         x:=fa[x];
         if x>=l then fa[x]:=l;
       end;
       dec(x);
     end;
   end;

 function check(m:longint):boolean;
   var s,i,j,x,y,k:longint;
   begin
     fillchar(fa,sizeof(fa),);
     s:=;
     for i:= to t do
       if q[i].id<=m then
       begin
         inc(s);
         a[s]:=i;
       end;

     i:=;
     while i<s do
     begin
       inc(i);
       j:=i+;
       while (j<=s) and (q[a[i]].mi=q[a[j]].mi) do inc(j);
       dec(j);
       x:=;
       y:=n+;
       for k:=i to j do
       begin
         x:=max(x,q[a[k]].x);
         y:=min(y,q[a[k]].y);
       end;
       if x>y then exit(false);
       if have(x,y) then exit(false);
       for k:=i to j do
         work(q[a[k]].x,q[a[k]].y);
       i:=j;
     end;
     exit(true);
   end;

 begin
   readln(n,t);
   for i:= to t do
   begin
     readln(q[i].x,q[i].y,q[i].mi);
     q[i].id:=i;
   end;
   sort(,t);
   l:=;
   r:=t-;
   if check(t) then writeln()
   else begin
     ans:=t;
     while l<=r do
     begin
       m:=(l+r) shr ;
       if not check(m) then
       begin
         ans:=m;
         r:=m-;
       end
       else l:=m+;
     end;
     writeln(ans);
   end;
 end.