hdu 2874 Connections between cities hdu 2586 How far away ？ LCA

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#include <cstdio>#include <cstring>#include <vector>#include <algorithm>using namespace std;#define maxn  10100struct Edge{    int u,v,w,next;}e[100100];int n,m,c;int head[maxn],cnt;int fa[maxn],cost[maxn],L[maxn];int anc[maxn][20];int parent[maxn];int find(int x){    if(parent[x]==x) return x;    else return parent[x]=find(parent[x]);}void add(int u,int v,int w){    e[cnt].u=u;    e[cnt].v=v;    e[cnt].w=w;    e[cnt].next=head[u];    head[u]=cnt++;}void dfs(int u,int father,int level){    int i;    L[u]=level;    for(i=head[u];i!=-1;i=e[i].next)    {        int v=e[i].v;        if(v!=father)        {            fa[v]=u;            cost[v]=cost[u]+e[i].w;            dfs(v,u,level+1);        }    }}void pre(){    int i,j;    for(i=0;i<n;i++)    {        anc[i][0]=fa[i];        for(j=1;(1<<j)<n;j++) anc[i][j]=-1;    }    for(j=1;(1<<j)<n;j++)        for(i=0;i<n;i++)        {            if(anc[i][j-1]!=-1)            {                int a=anc[i][j-1];                anc[i][j]=anc[a][j-1];            }        }}int query(int p,int q){    int tmp,log,i;    if(L[p]<L[q]) swap(p, q);    for(log=1;(1<<log)<=L[p];log++);log--;    int ans=-1000000000;    for(i=log;i>=0;i--)        if(L[p]-(1<<i)>=L[q])            p=anc[p][i];    if(p==q) return p;    for(i=log;i>=0;i--)    {        if(anc[p][i]!=-1&&anc[p][i]!=anc[q][i])        {            p=anc[p][i];            q=anc[q][i];        }    }    return fa[p];}int main(){    int i,j;    while(scanf("%d%d%d",&n,&m,&c)!=EOF)    {        memset(head,-1,sizeof(head));        cnt=0;        int x,y,z;        for(i=1;i<=n;i++) parent[i]=i;        for(i=1;i<=m;i++)        {            scanf("%d%d%d",&x,&y,&z);            add(x,y,z);            add(y,x,z);            int px=find(x);            int py=find(y);            if(px!=py) parent[px]=py;        }        for(i=1;i<=n;i++)            if(parent[i]==i)            {                add(0,i,0);                add(i,0,0);            }        n++;        cost[0]=0;        dfs(0,-1,0);        pre();        for(i=1;i<=c;i++)        {            scanf("%d%d",&x,&y);            if(find(x)!=find(y)) printf("Not connected\n");            else            {                int xx=query(x,y);                printf("%d\n",cost[x]+cost[y]-2*cost[xx]);            }        }    }    return 0;}

#pragma comment(linker, "/STACK:1000000000,1000000000")#include <cstdio>#include <cstring>#include <vector>#include <algorithm>using namespace std;#define maxn  40100struct Edge{    int u,v,w,next;}e[100100];int n,m;int head[maxn],cnt;int fa[maxn],cost[maxn],L[maxn];int anc[maxn][20];void add(int u,int v,int w){    e[cnt].u=u;    e[cnt].v=v;    e[cnt].w=w;    e[cnt].next=head[u];    head[u]=cnt++;}void dfs(int u,int father,int level){    int i;    L[u]=level;    for(i=head[u];i!=-1;i=e[i].next)    {        int v=e[i].v;        if(v!=father)        {            fa[v]=u;            cost[v]=cost[u]+e[i].w;            dfs(v,u,level+1);        }    }}void pre(){    int i,j;    for(i=0;i<n;i++)    {        anc[i][0]=fa[i];        for(j=1;(1<<j)<n;j++) anc[i][j]=-1;    }    for(j=1;(1<<j)<n;j++)        for(i=0;i<n;i++)        {            if(anc[i][j-1]!=-1)            {                int a=anc[i][j-1];                anc[i][j]=anc[a][j-1];            }        }}int query(int p,int q){    int tmp,log,i;    if(L[p]<L[q]) swap(p, q);    for(log=1;(1<<log)<=L[p];log++);log--;    int ans=-1000000000;    for(i=log;i>=0;i--)        if(L[p]-(1<<i)>=L[q])            p=anc[p][i];    if(p==q) return p;    for(i=log;i>=0;i--)    {        if(anc[p][i]!=-1&&anc[p][i]!=anc[q][i])        {            p=anc[p][i];            q=anc[q][i];        }    }    return fa[p];}int main(){    int cas,i,j;    scanf("%d",&cas);    while(cas--)    {        scanf("%d%d",&n,&m);        memset(head,-1,sizeof(head));        cnt=0;        int x,y,z;        for(i=1;i<n;i++)        {            scanf("%d%d%d",&x,&y,&z);            x--;            y--;            add(x,y,z);            add(y,x,z);        }        dfs(0,-1,0);        pre();        cost[0]=0;        for(i=1;i<=m;i++)        {            scanf("%d%d",&x,&y);            x--;y--;            int xx=query(x,y);            printf("%d\n",cost[x]+cost[y]-2*cost[xx]);        }    }    return 0;}

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