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[];bool bk,v[][];
void dfs(int k)
{
    if(bk==true)return ;
    if(k==D+)return ;
    if(x[k-]>n)return ;
    if(x[k-]==n)
    {
        bk=true;
        for(int i=;i<k-;i++)printf("%d ",x[i]);
        printf("%d\n",x[k-]);
        return ;
    }

    memset(v[k],false,sizeof(v[k]));
    for(int i=k-;i>=;i--)
    {
        if(x[i]+x[i]<x[k-])break;
        for(int j=i;j>=;j--)
        {
            if(x[i]+x[j]<x[k-])break;
            if(v[k][x[i]+x[j]]==false)
            {
                v[k][x[i]+x[j]]=true;
                x[k]=x[i]+x[j];
                dfs(k+);
                x[k]=;
            }
        }
    }
}
int main()
{
    while(scanf("%d",&n)!=EOF)
    {
        if(n==)break;

        D=;bk=false;x[]=;
        while()
        {
            dfs();
            if(bk==true)break;
            D++;
        }
    }
    return ;
}

poj2248

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[];
bool cmp(int x,int y){return x>y;}

int len;int a[];
inline void dfs(int k,int d)
{
    if(k==n/+)
    {
        a[++len]=d;
        return ;
    }
    if(((LL)d)+c[k]<=W)dfs(k+,d+c[k]);
    dfs(k+,d);
}
int mmax;
int erfen(int k)
{
    int l=,r=len;int ans;
    while(l<=r)
    {
        int mid=(l+r)/;
        if(a[mid]<=k)
        {
            ans=a[mid];
            l=mid+;
        }
        else r=mid-;
    }
    return ans;
}
inline void dfs2(int k,int d)
{
    if(k==n+)
    {
        mmax=max(mmax,d+erfen(W-d));return ;
    }

    if(((LL)d)+c[k]<=W)dfs2(k+,d+c[k]);
    dfs2(k+,d);
}
int main()
{
    scanf("%d%d",&W,&n);
    for(int i=;i<=n;i++)scanf("%d",&c[i]);
    sort(c+,c+n+,cmp);

    len=;dfs(,);
    sort(a+,a+len+);len=unique(a+,a+len+)-a-;
    mmax=a[len];
    dfs2(n/+,);
    printf("%d\n",mmax);
    return ;
}#include<cstdio>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<cmath>
using namespace std;
typedef long long LL;

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

int len;int a[];
inline void dfs(int k,int d)
{
    if(k==n/+)
    {
        a[++len]=d;
        return ;
    }
    if(((LL)d)+c[k]<=W)dfs(k+,d+c[k]);
    dfs(k+,d);
}
int mmax;
int erfen(int k)
{
    int l=,r=len;int ans;
    while(l<=r)
    {
        int mid=(l+r)/;
        if(a[mid]<=k)
        {
            ans=a[mid];
            l=mid+;
        }
        else r=mid-;
    }
    return ans;
}
inline void dfs2(int k,int d)
{
    if(k==n+)
    {
        mmax=max(mmax,d+erfen(W-d));return ;
    }

    if(((LL)d)+c[k]<=W)dfs2(k+,d+c[k]);
    dfs2(k+,d);
}
int main()
{
    scanf("%d%d",&W,&n);
    for(int i=;i<=n;i++)scanf("%d",&c[i]);
    sort(c+,c+n+,cmp);

    len=;dfs(,);
    sort(a+,a+len+);len=unique(a+,a+len+)-a-;
    mmax=a[len];
    dfs2(n/+,);
    printf("%d\n",mmax);
    return ;
}

送礼物