【解题思路】
直接上树剖套线段树/BIT即可。复杂度o(n+qlog22n)（线段树）或o(n+qlog23n)（BIT）。
【参考代码】
树剖套BIT。（这个树剖好naive啊QAQ）
1 #include <algorithm> 2 #include <cctype> 3 #include <cstdio> 4 #define REP(I,start,end) for(int I=(start);I<=(end);I++) 5 #define PER(I,start,end) for(int I=(start);I>=(end);I--) 6 #define ClearStack(_stack) while(!_stack.empty()){_stack.pop();} 7 #define ClearQueue(_queue) while(!_queue.empty()){_queue.pop();} 8 #define ClearArray(_array,from,to,val) REP(i,from,to){_array[i]=val;} 9 #define maxint 32767 10 #define maxlongint 2147483647 11 #define maxint64 9223372036854775807ll 12 inline void space() 13 { 14 putchar(' '); 15 } 16 inline void enter() 17 { 18 putchar(' '); 19 } 20 inline bool eoln(char ptr) 21 { 22 return ptr==' '; 23 } 24 inline bool eof(char ptr) 25 { 26 return ptr==' '; 27 } 28 inline int getint() 29 { 30 char ch=getchar(); 31 for(;!isdigit(ch)&&ch!='+'&&ch!='-';ch=getchar()); 32 bool impositive=ch=='-'; 33 if(impositive) 34 ch=getchar(); 35 int result=0; 36 for(;isdigit(ch);ch=getchar()) 37 result=(result<<3)+(result<<1)+ch-'0'; 38 return impositive?-result:result; 39 } 40 inline char *getstr() 41 { 42 char *result=new char[256],*ptr=result,ch=getchar(); 43 for(;isspace(ch)||eoln(ch)||eof(ch);ch=getchar()); 44 for(;!isspace(ch)&&!eoln(ch)&&!eof(ch);ch=getchar()) 45 { 46 *ptr=ch; 47 ptr++; 48 } 49 *ptr=' '; 50 return result; 51 } 52 template<typename integer> inline int write(integer n) 53 { 54 integer now=n; 55 bool impositive=now<0; 56 if(impositive) 57 { 58 putchar('-'); 59 now=-now; 60 } 61 char sav[20]; 62 sav[0]=now%10+'0'; 63 int result=1; 64 for(;now/=10;sav[result++]=now%10+'0'); 65 PER(i,result-1,0) 66 putchar(sav[i]); 67 return result+impositive; 68 } 69 template<typename T> inline bool getmax(T &target,T pattern) 70 { 71 return pattern>target?target=pattern,true:false; 72 } 73 template<typename T> inline bool getmin(T &target,T pattern) 74 { 75 return pattern<target?target=pattern,true:false; 76 } 77 template<typename T> class BIT 78 { 79 private: 80 int size; 81 T _nINF,_INF,*sav,*savSum,*savMax,*savMin; 82 int lowbit(int now) 83 { 84 return now&-now; 85 } 86 public: 87 inline void clear(int length,T nINF=-maxlongint,T INF=maxlongint) 88 { 89 size=length; 90 delete []sav; 91 delete []savSum; 92 delete []savMax; 93 delete []savMin; 94 sav=new T[size+1]; 95 savSum=new T[size+1]; 96 savMin=new T[size+1]; 97 savMax=new T[size+1]; 98 _nINF=nINF; 99 _INF=INF; 100 ClearArray(sav,1,size,0); 101 ClearArray(savSum,1,size,0); 102 ClearArray(savMax,1,size,_nINF); 103 ClearArray(savMin,1,size,_INF); 104 } 105 inline void increase(int point,T delta) 106 { 107 sav[point]+=delta; 108 for(int i=point;i<=size;i+=lowbit(i)) 109 { 110 savSum[i]+=delta; 111 savMax[i]=savMin[i]=sav[i]; 112 for(int j=1;j<lowbit(i);j<<=1) 113 { 114 getmax(savMax[i],savMax[i-j]); 115 getmin(savMin[i],savMin[i-j]); 116 } 117 } 118 } 119 inline void change(int point,T val) 120 { 121 T delta=val-sav[point]; 122 sav[point]=val; 123 for(int i=point;i<=size;i+=lowbit(i)) 124 { 125 savSum[i]+=delta; 126 savMax[i]=savMin[i]=sav[i]; 127 for(int j=1;j<lowbit(i);j<<=1) 128 { 129 getmax(savMax[i],savMax[i-j]); 130 getmin(savMin[i],savMin[i-j]); 131 } 132 } 133 } 134 inline T pre_sum(int length) 135 { 136 T result=T(0); 137 for(int i=length;i;i-=lowbit(i)) 138 result+=savSum[i]; 139 return result; 140 } 141 inline T query_sum(int left,int right) 142 { 143 return pre_sum(right)-pre_sum(left-1); 144 } 145 inline T query_max(int left,int right) 146 { 147 T result=sav[right]; 148 for(int l=left,r=right;l<r;) 149 { 150 for(r--;r-l>=lowbit(r);r-=lowbit(r)) 151 getmax(result,savMax[r]); 152 getmax(result,sav[r]); 153 } 154 return result; 155 } 156 inline T query_min(int left,int right) 157 { 158 T result=sav[right]; 159 for(int l=left,r=right;l<r;) 160 { 161 for(r--;r-l>=lowbit(r);r-=lowbit(r)) 162 getmin(result,savMin[r]); 163 getmin(result,sav[r]); 164 } 165 return result; 166 } 167 }; 168 //=============================Header Template=============================== 169 #include <cstring> 170 #include <vector> 171 using namespace std; 172 typedef vector<int> vecint; 173 BIT<int> bit[30010]; 174 int depth[30010],w[30010],father[30010],weight[30010],wfa[30010],wson[30010],group[30010],position[30010]; 175 vecint lines[30010]; 176 int DFS(int now) 177 { 178 weight[now]=1; 179 for(vecint::iterator i=lines[now].begin();i!=lines[now].end();i++) 180 { 181 int p=*i; 182 if(!weight[p]) 183 { 184 father[p]=now; 185 weight[now]+=DFS(p); 186 } 187 } 188 return weight[now]; 189 } 190 void DFSdep(int now,int deep) 191 { 192 if(!now) 193 return; 194 depth[now]=deep; 195 for(vecint::iterator i=lines[now].begin();i!=lines[now].end();i++) 196 { 197 int p=*i; 198 if(p!=father[now]&&p!=wson[now]) 199 DFSdep(p,deep+1); 200 } 201 DFSdep(wson[now],deep); 202 } 203 int main() 204 { 205 int n=getint(); 206 memset(lines,0,sizeof(lines)); 207 REP(i,2,n) 208 { 209 int u=getint(),v=getint(); 210 lines[u].push_back(v); 211 lines[v].push_back(u); 212 } 213 REP(i,1,n) 214 w[i]=getint(); 215 memset(weight,0,sizeof(weight)); 216 father[0]=father[1]=0; 217 DFS(1); 218 memset(wson,0,sizeof(wson)); 219 REP(i,1,n) 220 { 221 int maxer=0; 222 for(vecint::iterator j=lines[i].begin();j!=lines[i].end();j++) 223 { 224 int p=*j; 225 if(p!=father[i]&&getmax(maxer,weight[p])) 226 wson[i]=p; 227 } 228 } 229 int cnt=0; 230 DFSdep(1,1); 231 REP(i,1,n) 232 if(wson[father[i]]!=i) 233 { 234 cnt++; 235 int place=0; 236 for(int j=i;j;j=wson[j]) 237 { 238 wfa[j]=i; 239 group[j]=cnt; 240 position[j]=++place; 241 } 242 bit[cnt].clear(place); 243 for(int j=i;j;j=wson[j]) 244 bit[cnt].change(position[j],w[j]); 245 } 246 int q=getint(); 247 while(q--) 248 { 249 char *opt=getstr(); 250 int u=getint(),v=getint(); 251 if(!strcmp(opt,"CHANGE")) 252 bit[group[u]].change(position[u],v); 253 if(!strcmp(opt,"QSUM")) 254 { 255 int ans=0; 256 for(;depth[u]>depth[v];u=father[wfa[u]]) 257 { 258 int left=position[u],right=position[wfa[u]]; 259 if(left>right) 260 swap(left,right); 261 ans+=bit[group[u]].query_sum(left,right); 262 } 263 for(;depth[u]<depth[v];v=father[wfa[v]]) 264 { 265 int left=position[v],right=position[wfa[v]]; 266 if(left>right) 267 swap(left,right); 268 ans+=bit[group[v]].query_sum(left,right); 269 } 270 for(;wfa[u]!=wfa[v];u=father[wfa[u]],v=father[wfa[v]]) 271 { 272 int left=position[u],right=position[wfa[u]]; 273 if(left>right) 274 swap(left,right); 275 ans+=bit[group[u]].query_sum(left,right); 276 left=position[v];right=position[wfa[v]]; 277 if(left>right) 278 swap(left,right); 279 ans+=bit[group[v]].query_sum(left,right); 280 } 281 int left=position[u],right=position[v]; 282 if(left>right) 283 swap(left,right); 284 ans+=bit[group[u]].query_sum(left,right); 285 write(ans); 286 enter(); 287 } 288 if(!strcmp(opt,"QMAX")) 289 { 290 int ans=-maxlongint; 291 for(;depth[u]>depth[v];u=father[wfa[u]]) 292 { 293 int left=position[u],right=position[wfa[u]]; 294 if(left>right) 295 swap(left,right); 296 getmax(ans,bit[group[u]].query_max(left,right)); 297 } 298 for(;depth[u]<depth[v];v=father[wfa[v]]) 299 { 300 int left=position[v],right=position[wfa[v]]; 301 if(left>right) 302 swap(left,right); 303 getmax(ans,bit[group[v]].query_max(left,right)); 304 } 305 for(;wfa[u]!=wfa[v];u=father[wfa[u]],v=father[wfa[v]]) 306 { 307 int left=position[u],right=position[wfa[u]]; 308 if(left>right) 309 swap(left,right); 310 getmax(ans,bit[group[u]].query_max(left,right)); 311 left=position[v];right=position[wfa[v]]; 312 if(left>right) 313 swap(left,right); 314 getmax(ans,bit[group[v]].query_max(left,right)); 315 } 316 int left=position[u],right=position[v]; 317 if(left>right) 318 swap(left,right); 319 getmax(ans,bit[group[u]].query_max(left,right)); 320 write(ans); 321 enter(); 322 } 323 } 324 return 0; 325 }