首页 > 代码库 > hdu4671 思维构造
hdu4671 思维构造
http://acm.hdu.edu.cn/showproblem.php?pid=4671
Every time someone wants to execute queries on a certain database, he will send a request to the first server in the list. If it‘s dead, he will simply turn to the next one. Otherwise a working copy of the database is found, and this copy is called active.
Now, given N and M, Makomuno wants to find a permutation for each database which could assure that all servers are load-balanced. Moreover, Makomuno hopes the system will be load-balanced even if exactly one server is broken.
Note that if we call the number of active copies on i-th server Ai, then load-balanced means max∣Ai - Aj∣≤1 for any i and j in non broken servers set. We won‘t consider broken servers in this case.
Each test case has one line containing two integer N ( 2≤N≤100) and M ( 1≤M≤100).
5 3
2 4 3 1 5 1 5 4 2 3 3 5 2 4 1HintIn the sample test case, the active copies of these databases are on server 2,1 and 3 in normal state. A = {1,1,1,0,0} If server 1 or 3 has broken, server 5 will take its work. In case we lost server 2, the second database will use server 4 instead. A = {1,BROKEN,1,1,0} It‘s clear that in any case this system is load-balanced according to the plan in sample output.
/** hdu4671 思维构造 题目大意:有n台server和m个数据库,我们要用server执行数据库,对于每一个数据库被执行server的优先级为1~n的一个排列。每一个数据库仅仅执行一次, 问如何定义m个数据库的优先级,如果有一台server坏了的情况下仍然满足每台server的执行数据库的数量差不能大于1 解题思路:这个题是一个考验思维的题。当然答案有非常多。我仅仅要确定每一个数据库优先级最高和次高的就能够了。我们分两种情况来讨论: 1.n>=m 在这样的情况下1~m第一优先级的为1~m,第二优先级的为余下的随意(若n==m,则全部随意。要保证第一第二不能是一个数) 2.n<m 在这样的情况下1~m为1~n。再1~n。知道循环够m。第二优先级,我们对于第一优先级一样的放在一块考虑,从n~1循环(和第一反复就跳过)。 为什么这样呢?由于如果i坏了,那么第二优先级添加的还是各一个,仍保证是对的。注意要n~1循环,由于第m不一定是n的倍数。所以有i~n 可能会在第一优先级里少排一个,我们在第二优先级里要优先考虑,否则会出现有一个坏了的话差大于1的情况 */ #include <string.h> #include <stdio.h> #include <iostream> #include <algorithm> using namespace std; int n,m,a[105][2],flag[105]; int main() { while(~scanf("%d%d",&n,&m)) { if(n>=m) { for(int i=1;i<=m;i++) { a[i][0]=i; if(a[i][0]==n) a[i][1]=1; else a[i][1]=n; } } else { for(int i=1;i<=m;i++) { a[i][0]=(i%n==0)?
n:i%n; } for(int i=1;i<=n;i++) { int k=n; for(int j=1;j<=m;j++) { if(a[j][0]==i) { k=(k%n==0)?
n:k%n; if(k==i)k--; k=(k%n==0)?
n:k%n; a[j][1]=k--; // printf("??%d:%d\n",a[j][0],a[j][1]); } } } } for(int i=1;i<=m;i++) { //printf(">>%d %d\n",a[i][0],a[i][1]); } for(int i=1;i<=m;i++) { memset(flag,0,sizeof(flag)); printf("%d %d",a[i][0],a[i][1]); flag[a[i][0]]=flag[a[i][1]]=1; for(int j=1;j<=n;j++) { while(flag[j])j++; if(j>n)break; printf(" %d",j); flag[j]=1; } printf("\n"); } } return 0; } /** 3 14 answer: 1 3 2 2 3 1 3 2 1 1 2 3 2 1 3 3 1 2 1 3 2 2 3 1 3 2 1 1 2 3 2 1 3 3 1 2 1 3 2 2 3 1 */
hdu4671 思维构造