2017年衢州联赛 T2

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题目

题解

单调栈或单调序列 + 二分查找优化

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代码（Pascal）

var n,tot,ans:longint;    a,q:array[0..50005]of longint; procedure init;  var i,x:longint;   begin     assign(input,'skyline.in');reset(input);     assign(output,'skyline.out');rewrite(output);      readln(n);      for i:=1 to n do       readln(x,a[i]);    end; function find(x:longint):longint;  var l,r,mid:longint;   begin     l:=0;r:=tot;     while l<=r do      begin        mid:=(r+l+1) div 2;        if q[mid]<x then begin                           find:=mid;                           l:=mid+1;                          end                    else r:=mid-1;       end;    end; procedure main;  var i,j,t:longint;   begin     tot:=0;ans:=0;     for i:=1 to n do      begin        if a[i]=0 then begin                         tot:=0;                         continue;                        end;        t:=find(a[i]);        if t=tot then begin                        inc(ans);inc(tot);                        q[tot]:=a[i];                       end else        if q[t+1]=a[i] then tot:=t+1                       else begin                              inc(ans);                              tot:=t+1;                              q[tot]:=a[i];                             end;       end;   end; procedure print;  begin    write(ans);   close(input);close(output);  end; begin   init;   main;   print;  end.