截图于Donny_You的博客
1 #include<iostream> 2 #include<cstdio> 3 #include<set> 4 using namespace std; 5 const int maxn=1e5+7; 6 int n,ss,ans; 7 int val[maxn],sum[maxn]; 8 set < int > s; 9 struct Edge{ 10 int next,to; 11 }edge[maxn]; 12 int head[maxn],num,fa[maxn]; 13 void add(int from,int to){ 14 edge[++num].next=head[from]; 15 edge[num].to=to; 16 head[from]=num; 17 } 18 void dfs(int x){ 19 sum[x]=sum[fa[x]]+val[x]; 20 s.insert(sum[x]); 21 if(s.count(sum[x]-ss)) ans++; 22 for(int i=head[x];i;i=edge[i].next){ 23 int v=edge[i].to; 24 dfs(v); 25 } 26 s.erase(sum[x]); 27 } 28 int main(){ 29 cin>>n>>ss; 30 for(int i=1;i<=n;i++) cin>>val[i]; 31 for(int i=1;i<n;i++){ 32 int x,y;cin>>x>>y; 33 fa[y]=x; 34 add(x,y); 35 } 36 s.insert(0); 37 dfs(1); 38 cout<<ans<<endl; 39 return 0; 40 }
这个代码还没调出来：
1 #include<iostream> 2 #include<cstdio> 3 #include<bitset> 4 using namespace std; 5 const int maxn=1e5+7; 6 bitset<maxn>bt; 7 int n,s,sum,h=1,t=0,ans; 8 int val[maxn]; 9 struct Edge{ 10 int next,to; 11 }edge[maxn]; 12 int head[maxn],num,q[maxn]; 13 void add(int from,int to){ 14 edge[++num].next=head[from]; 15 edge[num].to=to; 16 head[from]=num; 17 } 18 void dfs(int u){ 19 cout<<u<<" "<<sum<<" "<<ans<<" "<<h<<" "<<t<<": "; 20 for(int i=h;i<=t;i++) cout<<q[i]<<" "; 21 cout<<endl; 22 if(sum==s){ 23 ans++; 24 if(head[u]){sum-=val[q[h]];h++;} 25 else return; 26 } 27 if(sum>s){ 28 int he=h,su=sum; 29 while(sum>s){ 30 sum-=val[q[h]];h++; 31 } 32 if(sum==s) { 33 ans++;cout<<"sum "<<sum<<" "; 34 sum-=val[q[h]];h++;cout<<sum<<endl; 35 } 36 if(sum<s) dfs(u); 37 h=he;sum=su; 38 } 39 if(head[u]==0) return; 40 int he=h,su=sum; 41 for(int i=head[u];i;i=edge[i].next){ 42 h=he;sum=su; 43 int v=edge[i].to; 44 q[++t]=v;sum+=val[v]; 45 dfs(v); 46 sum-=val[v];t--; 47 } 48 return; 49 } 50 int main(){ 51 cin>>n>>s; 52 for(int i=1;i<=n;i++) cin>>val[i]; 53 for(int i=1;i<n;i++){ 54 int x,y;cin>>x>>y;add(x,y); 55 } 56 sum=val[1];q[++t]=1;dfs(1); 57 cout<<ans<<endl; 58 return 0; 59 }