delete pics to save space

1.3819.cpp

@@ -0,0 +1,32 @@
+#include<cstdio>
+#include<algorithm>
+using namespace std;
+typedef long long LL;
+const int maxn=1e5+5;
+LL n,x[maxn],r[maxn],L,R,M1,M2,v1,v2,res;
+inline LL f(LL p)
+{
+	LL tot=0;
+	for(int i=1;i<=n;i++) tot+=abs(p-x[i])*r[i];
+//	printf("p=%lld tot=%lld\n",p,tot);
+	return tot;
+}
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	scanf("%lld%lld",&R,&n);
+	for(int i=1;i<=n;i++) scanf("%lld%lld",&x[i],&r[i]);
+	res=f(0);
+	while(R-L>3)
+	{
+		M1=(R-L)/3+L; M2=(R-L)/3*2+L;
+		v1=f(M1); v2=f(M2);
+		if(v1>=v2) L=M1,res=v2;
+		else R=M2,res=v1;
+	}
+	for(LL i=L;i<=R;i++) res=min(res,f(i));
+	printf("%lld\n",res);
+	return 0;
+}