思路
第一个可以倍增,第二个讨论在a到lca的路径上还是lca到b的路径上,
倍增即可
代码
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
int jump[10010][16],sum[10010][16],fir[10010],nxt[10010*2],v[10010*2],w[10010*2],cnt,dep[10010],n;
void addedge(int ui,int vi,int wi){
++cnt;
v[cnt]=vi;
w[cnt]=wi;
nxt[cnt]=fir[ui];
fir[ui]=cnt;
}
void dfs(int u,int f,int wx){
dep[u]=dep[f]+1;
jump[u][0]=f;
sum[u][0]=wx;
for(int i=1;i<15;i++)
jump[u][i]=jump[jump[u][i-1]][i-1],sum[u][i]=sum[u][i-1]+sum[jump[u][i-1]][i-1];
for(int i=fir[u];i;i=nxt[i]){
if(v[i]==f)
continue;
dfs(v[i],u,w[i]);
}
}
int lca(int x,int y){
if(dep[x]<dep[y])
swap(x,y);
for(int i=15;i>=0;i--)
if(dep[jump[x][i]]>=dep[y])
x=jump[x][i];
if(x==y)
return x;
for(int i=15;i>=0;i--)
if(jump[x][i]!=jump[y][i])
x=jump[x][i],y=jump[y][i];
return jump[x][0];
}
int query_sum(int x,int y){
int ans=0;
if(dep[x]<dep[y])
swap(x,y);
for(int i=15;i>=0;i--)
if(dep[jump[x][i]]>=dep[y]){
ans+=sum[x][i];
x=jump[x][i];
}
if(x==y)
return ans;
for(int i=15;i>=0;i--)
if(jump[x][i]!=jump[y][i]){
ans+=sum[x][i]+sum[y][i];
x=jump[x][i],y=jump[y][i];
}
return ans+sum[x][0]+sum[y][0];
}
int kth_fa(int x,int k){
for(int i=15;i>=0;i--){
if((k>>i)&1)
x=jump[x][i];
}
return x;
}
void init(void){
memset(jump,0,sizeof(jump));
memset(sum,0,sizeof(sum));
memset(fir,0,sizeof(fir));
memset(nxt,0,sizeof(nxt));
memset(v,0,sizeof(v));
memset(w,0,sizeof(w));
cnt=0;
memset(dep,0,sizeof(dep));
}
int main(){
int T;
scanf("%d",&T);
while(T--){
init();
scanf("%d",&n);
for(int i=1;i<n;i++){
int a,b,c;
scanf("%d %d %d",&a,&b,&c);
addedge(a,b,c);
addedge(b,a,c);
}
dfs(1,0,0);
char opt[10];
while(1){
scanf("%s",opt);
if(opt[1]=='O')
break;
if(opt[1]=='I'){
int a,b;
scanf("%d %d",&a,&b);
printf("%d
",query_sum(a,b));
}
else{
int a,b,c;
scanf("%d %d %d",&a,&b,&c);
int LCA=lca(a,b);
if(dep[a]-dep[LCA]+1>=c){
printf("%d
",kth_fa(a,c-1));
}
else{
c-=dep[a]-dep[LCA];
int t2=dep[b]-dep[LCA]+1;
printf("%d
",kth_fa(b,t2-c));
}
}
}
}
return 0;
}