47 lines
1.1 KiB
C++
47 lines
1.1 KiB
C++
#include <cstdio>
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#include <cstring>
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#include <algorithm>
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using namespace std ;
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#define LL __int64
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LL dp[50100] ;
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int a[50100] ;
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LL gcd(LL a,LL b) {
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return b == 0 ? a : gcd(b,a%b) ;
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}
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int main() {
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int t , n , m ;
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int i , l , r ;
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LL x , y , temp ;
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scanf("%d", &t) ;
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while( t-- ) {
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scanf("%d %d", &n, &m) ;
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memset(dp,0,sizeof(dp)) ;
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for(i = 1 ; i <= n ; i++)
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scanf("%d", &a[i]) ;
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while( m-- ) {
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scanf("%d %d", &l, &r) ;
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dp[l]++ ;
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dp[r+1]-- ;
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}
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x = 0 ;
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y = (LL)n*(n-1)*(n-2)/6 ;
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for(i = 1 ; i <= n ; i++) {
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dp[i] += dp[i-1] ;
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if( dp[i] > 2 )
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x += dp[i]*(dp[i]-1)*(dp[i]-2)/6*a[i] ;
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}
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if( x == 0 || y == 0 ) {
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printf("0\n") ;
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continue ;
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}
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temp = gcd(x,y) ;
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x /= temp ;
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y /= temp ;
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if( y == 1 )
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printf("%I64d\n", x ) ;
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else
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printf("%I64d/%I64d\n", x, y) ;
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}
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return 0 ;
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}
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