0x22 迭代加深

poj2248 真是个新套路。还有套路剪枝...大到小和判重

#include<cstdio>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<cmath>
#include<bitset>
using namespace std;

int n,D,x[110];bool bk,v[110][110];
void dfs(int k)
{
    if(bk==true)return ;
    if(k==D+1)return ;
    if(x[k-1]>n)return ;
    if(x[k-1]==n)
    {
        bk=true;
        for(int i=1;i<k-1;i++)printf("%d ",x[i]);
        printf("%d\n",x[k-1]);
        return ;
    }
    
    memset(v[k],false,sizeof(v[k]));
    for(int i=k-1;i>=1;i--)
    {
        if(x[i]+x[i]<x[k-1])break;
        for(int j=i;j>=1;j--)
        {
            if(x[i]+x[j]<x[k-1])break;
            if(v[k][x[i]+x[j]]==false)
            {
                v[k][x[i]+x[j]]=true;
                x[k]=x[i]+x[j];
                dfs(k+1);
                x[k]=0;
            }
        }
    }
}
int main()
{
    while(scanf("%d",&n)!=EOF)
    {
        if(n==0)break;
    
        D=1;bk=false;x[1]=1;
        while(1)
        {
            dfs(2);
            if(bk==true)break;
            D++;
        }
    }
    return 0;
}

送礼物 折半搜索（orz cgh队长之前教我），书上叫双向搜索。又双叒叕有套路剪枝...大到小和很明显的可行性。结果dfs时居然还要先尝试选再尝试不选。。无语

#include<cstdio>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<cmath>
using namespace std;
typedef long long LL;

int n;int W,c[110];
bool cmp(int x,int y){return x>y;}

int len;int a[10001000];
inline void dfs(int k,int d)
{
    if(k==n/2+1)
    {
        a[++len]=d;
        return ;
    }
    if(((LL)d)+c[k]<=W)dfs(k+1,d+c[k]);
    dfs(k+1,d);
}
int mmax;
int erfen(int k)
{
    int l=1,r=len;int ans;
    while(l<=r)
    {
        int mid=(l+r)/2;
        if(a[mid]<=k)
        {
            ans=a[mid];
            l=mid+1;
        }
        else r=mid-1;
    }
    return ans;
}
inline void dfs2(int k,int d)
{
    if(k==n+1)
    {
        mmax=max(mmax,d+erfen(W-d));return ;
    }
    
    if(((LL)d)+c[k]<=W)dfs2(k+1,d+c[k]);
    dfs2(k+1,d);
}
int main()
{
    scanf("%d%d",&W,&n);
    for(int i=1;i<=n;i++)scanf("%d",&c[i]);
    sort(c+1,c+n+1,cmp);
    
    len=0;dfs(1,0);
    sort(a+1,a+len+1);len=unique(a+1,a+len+1)-a-1;
    mmax=a[len];
    dfs2(n/2+1,0);
    printf("%d\n",mmax);
    return 0;
}#include<cstdio>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<cmath>
using namespace std;
typedef long long LL;

int n;int W,c[110];
bool cmp(int x,int y){return x>y;}

int len;int a[10001000];
inline void dfs(int k,int d)
{
    if(k==n/2+1)
    {
        a[++len]=d;
        return ;
    }
    if(((LL)d)+c[k]<=W)dfs(k+1,d+c[k]);
    dfs(k+1,d);
}
int mmax;
int erfen(int k)
{
    int l=1,r=len;int ans;
    while(l<=r)
    {
        int mid=(l+r)/2;
        if(a[mid]<=k)
        {
            ans=a[mid];
            l=mid+1;
        }
        else r=mid-1;
    }
    return ans;
}
inline void dfs2(int k,int d)
{
    if(k==n+1)
    {
        mmax=max(mmax,d+erfen(W-d));return ;
    }
    
    if(((LL)d)+c[k]<=W)dfs2(k+1,d+c[k]);
    dfs2(k+1,d);
}
int main()
{
    scanf("%d%d",&W,&n);
    for(int i=1;i<=n;i++)scanf("%d",&c[i]);
    sort(c+1,c+n+1,cmp);
    
    len=0;dfs(1,0);
    sort(a+1,a+len+1);len=unique(a+1,a+len+1)-a-1;
    mmax=a[len];
    dfs2(n/2+1,0);
    printf("%d\n",mmax);
    return 0;
}