Codeforces1063d candies for Children [Classification discussion] [violence]

Source: Internet
Author: User

Question Analysis:

First, consider two brute force attacks. The time complexity of one is $ O (N ^ 2) $, and the other is $ O ([\ frac {n} {k}] $.

$ N ^ 2 $ violence can be enumerated in two sections, one for $ I $ and the other for $ J $.

You can calculate the cost of selecting them in each round, for example, $ Alpha $ and $ beta $. All you have to do is solve $ (x + 1) * Alpha + x * Beta = K $, which is not hard to solve.

 

Then there is $ O ([\ frac {n} {k}]) $ violence, enumerating the number of rounds of the election, that is, the above $ x $. Assume that each child chooses a candy, and the problem becomes that the child chooses or does not select a candy.

The new parameter $ gamma $ is introduced to indicate the number of sweets you need to select.

It is not difficult to find a group of solutions $ (gamma,-gamma) $. Then the Selection Range of the two solutions is $[0 or 1, len1] $ and $ [0, len2] $. Just tune it.

 

Code:

 1 #include<bits/stdc++.h> 2 using namespace std; 3  4 long long n,l,r,k; 5  6 long long func(long long x,long long y,long long ki,int dr,long long ll,long long rr){ 7     if(y == 0){ 8     if(ki == 0 && dr == -1) return -1; 9     if(ki <= ll) return ki+rr;10     else return -1;11     }12     long long a = ki,b = -ki;13     long long hh = a/y;a %= y; b += hh*x;14     if(a > ll) return -1;15     if(dr == 1){16     if(b < 0) return -1;17     if(b <= rr)return b+a;18     else {19         hh = (b-rr)/x+((b-rr)%x!=0);20         b -= hh*x;21         a += hh*y;22         if(a <= ll) return b+a;23         else return -1;24     }25     }else{26     if(a == 0) a += y,b -= x;27     if(b < 0) return -1;28     if(b <= rr) return b+a;29     else {30         hh = (b-rr)/x+((b-rr)%x!=0);31         b -= hh*x;32         a += hh*y;33         if(a <= ll) return b+a;34         else return -1;35     }36     }37 }38 39 int main(){40     scanf("%I64d%I64d%I64d%I64d",&n,&l,&r,&k);41     long long um = (r-l+n)%n;42     l = 1; r = 1+um;43     if(k/n <= 5e6){44     long long len1 = r-l+1,len2 = n-len1;45     long long ans = -1;46     for(int i=0;i<=k/n;i++){47         long long zeta = k-i*n-len1;48         if(zeta>=0)ans = max(ans,func(i+1,i,zeta,1,len1,len2));49         zeta = k+1-i*n-len1;50         if(zeta>=0)ans = max(ans,func(i+1,i,zeta,-1,len1,len2));51     }52     printf("%I64d",ans);53     }else{54     int len1 = r-l+1,len2 = n-len1;55     int ans = -1;56     for(int i=0;i<=len1;i++){57         for(int j=0;j<=len2;j++){58         int alpha = len1+i,beta = len2+j;59         long long zeta = k-alpha;60         if(zeta % (alpha+beta) == 0) ans = max(ans,i+j);61         }62     }63     k++;64     for(int i=1;i<=len1;i++){65         for(int j=0;j<=len2;j++){66         int alpha = len1+i,beta = len2+j;67         long long zeta = k-alpha;68         if(zeta % (alpha+beta) == 0) ans = max(ans,i+j);69         }70     }71     printf("%d",ans);72     }73     return 0;74 }

 

Codeforces1063d candies for Children [Classification discussion] [violence]

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.