第十二届蓝桥杯 砝码称重

暴搜 只能过50%

import java.util.*;

public class Main
{
	static int n,N=100005,ans;
	static boolean st[]=new boolean [N];
	static boolean us[]=new boolean [N];
	static int a[]=new int [N];
	
	static void dfs(int t,int from,int p)
	{
		if(t==n+1)return;
		for(int i=from;i<n;++i)
		{
			if(us[i]==false)
			{
				us[i]=true;
				int d=Math.abs(p-a[i]);
				
				st[p+a[i]]=true;
				dfs(t+1,i+1,p+a[i]);
				st[d]=true;
				dfs(t+1,i+1,d);
				
				us[i]=false;
			}
		}
		
	}
	
	public static void main(String args[])
	{
		Scanner sc=new Scanner(System.in);
		n=sc.nextInt();
		for(int i=0;i<n;++i)
		{
			a[i]=sc.nextInt();st[a[i]]=true;
		}
		dfs(1,0,0);
		for(int i=1;i<N;++i)
			if(st[i])ans++;
		System.out.println(ans);
	}
}

模拟可以AC,因为给定条件说了砝码总的重量在10^5内

import java.util.*;

public class Main
{
	static int n,N=100005,ans;
	static boolean st[]=new boolean [N],backup[]=new boolean[N];
	static int a[]=new int [N];
	
	public static void main(String args[])
	{
		Scanner sc=new Scanner(System.in);
		n=sc.nextInt();
		
		for(int i=0;i<n;++i)
		{
			a[i]=sc.nextInt();
		}
		
		for(int i=0;i<n;++i)
		{
			backup=st.clone();
			for(int j=1;j<N;++j)
			{
				if(backup[j]==true)
				{
					int d=Math.abs(j-a[i]);
					st[j+a[i]]=true;
					st[d]=true;
				}
			}
			st[a[i]]=true;
		}
		for(int i=1;i<N;++i)
			if(st[i])ans++;
		System.out.println(ans);
	}
}

DP

import java.util.*;

public class Main
{
	static int N=105,M=200005,S=M/2;
	static boolean f[][]=new boolean [N][M];
	static int w[]=new int [N];
	static int n,m,ans;
	
	public static void main(String args[])
	{
		Scanner sc=new Scanner(System.in);
		n=sc.nextInt();
		
		for(int i=1;i<=n;++i)
		{
			w[i]=sc.nextInt();
			m+=w[i];
		}
		
		f[0][S]=true;
		
		for(int i=1;i<=n;++i)
		{
			for(int j=-m;j<=m;++j)
			{
				
				f[i][j+S]=f[i-1][j+S];
				if(j-w[i]+S>=0)f[i][j+S]|=f[i-1][j+S-w[i]];
				if(j+w[i]+S<M)f[i][j+S]|=f[i-1][j+S+w[i]];
			}
		}
		for(int i=1;i<=m;++i)
			if(f[n][i+S])ans++;
		
		System.out.println(ans);
	}
}