树形dp,注意赋初值
1 #include <bits/stdc++.h> 2 using namespace std; 3 #define rep(i,a,b) for(int i=a;i<=b;++i) 4 #define fgr(i,u) for(int i=head[u];i;i=to[i]) 5 #define fd(i,a,b) for(int i=a;i>=b;--i) 6 const int maxn=5010; 7 template <typename T> inline bool check_Max(T &x,const T&y) {return x<y?x=y,false:true;} 8 template <typename T> inline bool check_Min(T &x,const T&y) {return x>y?x=y,false:true;} 9 inline int gi() { 10 int x=0; char o; bool f=true; for(;!isdigit(o=getchar());)if(o=='-')f=false; 11 for(;isdigit(o);o=getchar()) x=(x<<1)+(x<<3)+(o&15); return f?x:~x+1; 12 } 13 int v[maxn<<1],to[maxn<<1],head[maxn],p; 14 inline void link(int a,int b){v[++p]=b; to[p]=head[a]; head[a]=p;} 15 int sz[maxn],col[maxn],Tx[maxn],Tn[maxn],g[maxn][maxn],f[maxn][maxn]; 16 int n,m; 17 inline void dfs(int u,int pre) { 18 sz[u]=1; g[u][1]=f[u][1]=col[u]; 19 fgr(i,u) if(v[i]^pre) { 20 dfs(v[i],u); 21 fd(j,sz[u],1) fd(k,sz[v[i]],1) 22 check_Max(f[u][j+k],f[u][j]+f[v[i]][k]), check_Min(g[u][j+k],g[u][j]+g[v[i]][k]); 23 sz[u]+=sz[v[i]]; 24 } 25 rep(i,1,n) check_Max(Tx[i],f[u][i]),check_Min(Tn[i],g[u][i]); 26 } 27 int T; 28 int main() { 29 #ifndef ONLINE_JUDGE 30 freopen("1.in","r",stdin); 31 #endif 32 T=gi(); 33 while(T--) { 34 n=gi(); m=gi(); 35 memset(f,0xc0,sizeof(f)); memset(g,0x3f,sizeof(g)); memset(head,0,sizeof(head)); 36 memset(Tn,0x3f,sizeof(Tn)); memset(Tx,0xc0,sizeof(Tx)); p=0; 37 //printf("%d\n",f[0][0]);//de bug 38 rep(i,2,n) {int u=gi(),v=gi(); link(u,v); link(v,u);} 39 rep(i,1,n) col[i]=gi(); 40 dfs(1,0); 41 rep(i,1,m) {int x=gi(),y=gi(); Tx[x]>=y&&Tn[x]<=y?puts("YES"):puts("NO");} 42 puts(""); 43 } 44 return 0; 45 }