0x22 迭代加深
poj2248 真是个新套路。还有套路剪枝...大到小和判重
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#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
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#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; }
pain and happy in the cruel world.