这个wqs二分并不熟练……
题目描述
题目分析
两维都用wqs二分，其他没有什么特殊之处。
重点在于，wqs二分还原最优解的时候，增量是强制给的k。
1 #include<bits/stdc++.h> 2 const int maxn = 100035; 3 const double eps = 1e-9; 4 5 int n,a,b,usa,usb; 6 double bet,ans,coa,cob,p[maxn],q[maxn]; 7 8 bool match() 9 { 10 double k1=coa,k2=cob; 11 usa = usb = 0, ans = 0; 12 for (int i=1, opt=0; i<=n; i++) 13 { 14 double v = 0;opt=0; 15 if (p[i]-k1 > v) opt = 1, v = p[i]-k1; 16 if (q[i]-k2 > v) opt = 2, v = q[i]-k2; 17 if (p[i]+q[i]-p[i]*q[i]-k1-k2 > v) 18 opt = 3, v = p[i]+q[i]-p[i]*q[i]-k1-k2; 19 if (opt==1||opt==3) usa++; 20 if (opt==2||opt==3) usb++; 21 ans += v; 22 } 23 return usb <= b; 24 } 25 bool check() 26 { 27 double l = 0, r = 1.0, bet; 28 for (cob=(l+r)/2.0; r-l>eps; cob=(l+r)/2.0) 29 if (match()) bet = r = cob; 30 else l = cob; 31 cob = bet; 32 match(); 33 return usa <= a; 34 } 35 int main() 36 { 37 while (scanf("%d%d%d",&n,&a,&b)!=EOF) 38 { 39 for (int i=1; i<=n; i++) scanf("%lf",&p[i]); 40 for (int i=1; i<=n; i++) scanf("%lf",&q[i]); 41 double l = 0, r = 1.0; 42 for (coa=(l+r)/2.0; r-l>eps; coa=(l+r)/2.0) 43 if (check()) bet = coa, r = coa; 44 else l = coa; 45 coa = bet; 46 check(); 47 ans += 1.0*a*coa+1.0*b*cob; //这里补偿答案用a,b 48 printf("%.5lf ",ans); 49 } 50 return 0; 51 }
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