Bzoj1113: [poi2008] Poster PLA

1113: [poi2008] Poster platime limit: 10 sec memory limit: 162 MB
Submit: 691 solved: 412
[Submit] [Status] Descriptionn rectangles in a row. now we want to cover them with a small number of rectangular posters. the first line of input gives the number N, which indicates that there are n rectangles. N is in N rows under [], and each row gives the length and width of the rectangle. the number of posters with a value of [1, 1/2] 2 posteringoutput is the minimum. sample input5
1 2
1 3
2 2
2 5
1 4


Sample output4


Hint Source

Question:

Ans can be equal to N at most. Under what circumstances can ans be reduced?

First, if it is reduced, it must have been pasted with a poster covering two rectangles with the same height (the width is soy sauce ...)

Then, if H [I] = H [J], we must ensure that there is no lower height between I and j than they are.

Why? Think of something, right, monotonous stack! Maintain a monotonically decreasing stack. When the element is equal to the top element of the stack, ANS -- and stack the top element.

Code:

 1 var top,ans,i,n:longint; 2     a,sta:array[0..260000] of longint; 3 procedure init; 4  begin 5    readln(n); 6    for i:=1 to n do readln(a[i],a[i]); 7  end; 8 procedure main; 9  begin10    top:=0;ans:=n;11    a[n+1]:=-1;12    for i:=1 to n+1 do13     begin14       while (top>0) and (a[i]<=a[sta[top]]) do15        begin16          if a[i]=a[sta[top]] then dec(ans);dec(top);17        end;18       inc(top);sta[top]:=i;19     end;20    writeln(ans);21  end;22 begin23   assign(input,‘input.txt‘);assign(output,‘output.txt‘);24   reset(input);rewrite(output);25   init;26   main;27   close(input);close(output);28 end.  

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