delete pics to save space

history_source/挑战程序设计竞赛/3.1.4.cpp

@@ -0,0 +1,41 @@
+#include<cstdio>
+#include<algorithm>
+using namespace std;
+int n,k,w[10005],v[10005];
+double y[10005];
+void init()
+{
+	scanf("%d%d",&n,&k);
+	for(int i=0;i<n;i++) scanf("%d%d",w+i,v+i);
+}
+bool C(double x)
+{
+	for(int i=0;i<n;i++) y[i]=v[i]-x*w[i];
+	sort(y,y+n);
+	double sum=0;
+	for(int i=0;i<k;i++) sum+=y[n-i-1];
+	return sum>=0;
+}
+void solve()
+{
+	double l=0,r=1000010,mid;
+	for(int i=0;i<100;i++)
+	{
+		mid=(l+r)/2;
+		if(C(mid)) l=mid;
+		else r=mid;
+	}
+	printf("%.2f\n",r);
+}
+int main()
+{
+	init();
+	solve();
+	return 0;
+}
+/*
+3 2
+2 2
+5 3
+2 1
+*/