text: create an array maxfromEnd
code: for ( int i = v . size ( ) - 1 ; i >= 0 ; i -- ) { maxFromEnd [ i ] = max ( maxFromEnd [ i + 1 ] , v [ i ] ) ; } int result = 0 ; for ( int i = 0 ; i < v . size ( ) ; i ++ ) { int low = i + 1 , high = v . size ( ) - 1 , ans = i ; while ( low <= high ) { int mid = ( low + high ) / 2 ; if ( v [ i ] <= maxFromEnd [ mid ] ) {