linux

/*



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  * PKU2081.cpp


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  *


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  *  Created on: 2011-3-19


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  *      Author: Administrator


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*/



 7
 


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 #include 
<
stdio.h
>



 9
  
//
#include <set>



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#include 
<
ext
/
hash_set
>



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using
 
namespace
 std;


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 using
 
namespace
 __gnu_cxx;


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 const
 
int
 MAXK 
=
 
500000
 
+
 
1
;


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 //
set<int> s1;



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 hash_set
<
int
>
 s1;


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 int
 a[MAXK];


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 int
 main () {


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     a[
0
] 
=
 
0
;


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     s1.insert(a[
0
]);


23
 


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for
 (
int
 i 
=
 
1
; i 
<=
 MAXK; i
++
) {


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         a[i] 
=
 a[i
-
1
] 
-
 i;


26
         
if
 (a[i] 
>
 
0
 
&&
 s1.find(a[i]) 
==
 s1.end())


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             ;


28
         
else



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             a[i] 
=
 a[i
-
1
] 
+
 i;


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         s1.insert(a[i]);


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     }


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 //
    for (int i = 0; i < 20; i++)


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 //
        printf("%d: %d/n", i, a[i]);



36
     
while
 (
true
) {


37
         
int
 n;


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         scanf(
"
%d
"
, 
&
n);


39
         
if
 (n 
==
 
-
1
)


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break
;


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         printf(
"
%d/n
"
, a[n]);


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     }


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return
 
0
;


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 }

头文件:

#include <ext/hash_set>

#include <ext/hash_map>

命名空间：

using namespace __gnu_cxx;