Codeforces 500C New Year Book Reading

C. New Year Book Reading

time limit per test
2 seconds

memory limit per test
256 megabytes

input
standard input

output
standard output

New Year is coming, and Jaehyun decided to read many books during 2015, unlike this year. He has n books numbered by integers from 1 to n. The weight of the i-th (1 ≤ i ≤ n) book is wi.

As Jaehyun's house is not large enough to have a bookshelf, he keeps the n books by stacking them vertically. When he wants to read a certain book x, he follows the steps described below.

He lifts all the books above book x.

He pushes book x out of the stack.

He puts down the lifted books without changing their order.

After reading book x, he puts book x on the top of the stack.

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N = 1010;

int n , m , w
, d
;
bool vis
;
int main()
{
while( cin >> n >> m ) {
for( int i = 1 ; i <= n ; ++i ) cin >> w[i] ;
for( int i = 1 ; i <= m ; ++i ) cin >> d[i] ;
LL ans = 0 ;
for( int i = 1 ; i <= m ; ++i ) {
memset( vis , false , sizeof vis );
for( int j = i - 1 ; j > 0 ; --j ){
if( d[i] == d[j] ) break ;
if( !vis[ d[j] ] ) { ans += w[ d[j] ] ; vis[ d[j] ] = true ; }
}
}
cout << ans << endl ;
}
}

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