33 lines
979 B
ObjectPascal
33 lines
979 B
ObjectPascal
var
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a,b,t,h,n,i:integer;
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q,d,k:array[1..1000]of integer; //q为队列，k为楼层数字，d为乘电梯次数
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s:set of 1..200; //到过楼层放入集合
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begin
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assign(input,'lift.in');reset(input);
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assign(output,'lift.out');rewrite(output);
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read(n,a,b);
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for i:=1 to n do
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read(k[i]);
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h:=0; //队头指针
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t:=1; //队尾指针
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q[1]:=a;
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repeat
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inc(h);
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for i:=-1 to 1 do //上楼或下楼
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if (q[h]+k[q[h]]*i>0) and not (q[h]+k[q[h]]*i in s) then
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begin //满足楼层要求且没到过
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inc(t);
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s:=s+[q[h]+k[q[h]]*i]; //放入集合
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q[t]:=q[h]+k[q[h]]*i; //入队
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d[t]:=d[h]+1; //记录乘电梯次数
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end;
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until (h=t) or (q[t]=b);
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if a=b then
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writeln(0)
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else
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if q[t]=b then //到达指定楼层
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writeln(d[t])
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else
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writeln('-1'); //无法到达
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close(input);close(output);
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end. |