poj 2763 LCA

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#include<cstdio>#include<cstring>#include<algorithm>#define MAX_N 100010using namespace std;struct point{int to,next,id;}G[MAX_N];int head[MAX_N],depth[MAX_N],bit[MAX_N],in[MAX_N],out[MAX_N],parent[21][MAX_N],vs[MAX_N],val[MAX_N];int cnt,k;void add_edge(int from,int to,int id){G[cnt].to=to;G[cnt].id=id;G[cnt].next=head[from];head[from]=cnt++;}void dfs(int v,int p,int d){depth[v]=d;parent[0][v]=p;for(int i=1;i<20;i++){if(parent[i][v]==-1)parent[i][v]=-1;elseparent[i][v]=parent[i-1][parent[i-1][v]]; }for(int i=head[v];i!=-1;i=G[i].next){point &e=G[i];if(e.to==p)continue;in[e.id]=vs[e.to]=++k;dfs(e.to,v,d+1);out[e.id]=++k;}}int LCA(int u,int v){if(depth[u]>depth[v])swap(u,v);for(int k=0;k<20;k++){if((depth[v]-depth[u])>>k&1)v=parent[k][v];}if(u==v)return u;for(int k=19;k>=0;k--){if(parent[k][u]!=parent[k][v]){u=parent[k][u];v=parent[k][v];}}return parent[0][v];}int sum(int i){int res=0;while(i>0){res+=bit[i];i-=i&-i;}return res;} void add(int i,int v){while(i<=k){bit[i]+=v;i+=i&-i;}}int main(){memset(head,-1,sizeof(head));cnt=k=0;int n,m;scanf("%d%d",&n,&m);for(int i=1;i<=m;i++){int a,b,c;char str[100];scanf("%d%d%d%s",&a,&b,&c,str);add_edge(a,b,i);add_edge(b,a,i);val[i]=c;}dfs(1,-1,0);memset(bit,0,sizeof(bit));for(int i=1;i<=m;i++){add(in[i],val[i]);add(out[i],-val[i]);}int Q;scanf("%d",&Q);while(Q--){int a,b;scanf("%d%d",&a,&b);printf("%d\n",sum(vs[a])+sum(vs[b])-2*sum(vs[LCA(a,b)]));}}
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