3122.txt

北大ACM题目例程 详细的解答过程 程序实现 算法分析

Source

Problem Id:3122  User Id:fzk 
Memory:72K  Time:31MS
Language:C++  Result:Accepted

Source 

#include <stdio.h>
#include <memory.h>

int main( ) {
	int r[10000], t, i, n, f, count;
	double a, b, c;

	scanf( "%d", &t );
	while( t-- ) {
		scanf( "%d%d", &n, &f );
		f++;
		b = 0;
		for( i=0; i<n; i++ ) {
			scanf( "%d", &r[i] );
			r[i] *= r[i];
			b += r[i];
		}

		a = 0;
		while( b-a> 1e-5 ) {
			c = (b+a)/2;
			count = 0;
			for( i=0; i<n; i++ )
				count += int(r[i]/c);
			if( count >= f )
				a = c;
			else
				b = c;
		}
		printf( "%.4lf\n", a*3.14159265358979324 );
	}
	return 0;
}