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Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 1329 Accepted Submission(s): 783
For each testcase, there are two lines:
1. The first line contains two integers n and a (1≤n≤20,1≤a≤106).
2. The second line contains n integers b1,…,bn (∀1≤i≤n,1≤bi≤106).
題意:給你20個數和a,a對這20個數進行取模,問最少需要多少個數使得取模爲0。
因爲只有20個數,那麼我直接暴力DFS就行,這裏有一個細節,如果a<b,那麼a%b=a,也就是說小數對大數取模,答案還是小數,也就相當於沒有取模但是多用了一個數,那麼我們就排除掉這種情況,使得每次取模都是有意義的,就能過了;
#include<stdio.h>
#include<string.h>
#include<map>
#include<algorithm>
using namespace std;
int a,flag;
int n;
int b[30];
int use[30];
void dfs(int sum,int m)
{
if(flag==1)
return;
if(sum<0)
return;
if(sum==0&&m==0)
flag=1;
for(int i=1;i<=n;i++)
{
if(use[i]==0&&b[i]<=m)
{
use[i]=1;
dfs(sum-1,m%b[i]);
use[i]=0;
}
}
}
int main()
{
int t;
scanf("%d",&t);
while(t--)
{
scanf("%d%d",&n,&a);
for(int i=1;i<=n;i++)
scanf("%d",&b[i]);
int ans=-1;
for(int i=1;i<=n;i++)
{
memset(use,0,sizeof(use));
flag=0;
dfs(i,a);
if(flag==1)
{
ans=i;
break;
}
}
printf("%d\n",ans);
}
return 0;
}