【CF912E】Prime Game（meet in the middle)

【CF912E】Prime Game（meet in the middle)

题面

CF
懒得翻译了。

题解

一眼题。
\(meet\ in\ the\ middle\)分别爆算所有可行的两组质数，然后二分答案，\(two-pointers\)扫一下就好了。

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
using namespace std;
#define ll long long
#define MAX 262145
inline int read()
{
    int x=0;bool t=false;char ch=getchar();
    while((ch<'0'||ch>'9')&&ch!='-')ch=getchar();
    if(ch=='-')t=true,ch=getchar();
    while(ch<='9'&&ch>='0')x=x*10+ch-48,ch=getchar();
    return t?-x:x;
}
int n,m,k;
int s1[MAX],s2[MAX],t1,t2;
void dfs1(int x,int s)
{
    if(x==k+1){s1[++t1]=s;return;}
    dfs1(x+1,s);dfs1(x+1,(s+a[i])%m);
}
void dfs2(int x,int s)
{
    if(x==n+1){s2[++t2]=s;return;}
    dfs2(x+1,s);dfs2(x+1,(s+a[i])%m);
}
int main()
{
    n=read();m=read();k=(n+1)/2;
    for(int i=1;i<=n;++i)a[i]=read();
    dfs1(1,0);dfs2(k+1,0);
    sort(&s1[1],&s1[t1+1]);sort(&s2[1],&s2[t2+1]);
    return 0;
}