noip2013day1题解

来源：互联网发布：linux的syslog开启编辑：程序博客网时间：2024/05/24 06:02

转圈游戏：

# include <iostream># include <algorithm># include <string># include <cstring># include <cmath># include <ctime># include <cstdio># include <queue>using namespace std; typedef long long ll;long long n,m,k,x;  ll Read(){ll i=0,f=1;char c=getchar();whi

#include<iostream> #include<cstdio>#include<cstdlib>#include<cstring>#include<cmath>#include<algorithm>using namespace std;#define MAXN 10010#define MAXM 50010#define MAXD 22#define inf 200000int father[MAXN],n,m,q;bool visit[MAXN];int up[MAXN][MAXD],Min[MAXN][MAXD],h[MAXN];struct saver{    int s,t,d;} e[MAXM]; int cmp(saver a,saver b){    return a.d>b.d;} //并查集void init()   {    for(int i=0; i<MAXN; i++)father[i]=i;}int Find(int x){    if(x==father[x])return father[x];    else    {        father[x]=Find(father[x]);        return father[x];    }}void Union(int x,int y){    int fx=Find(x);    int fy=Find(y);    if(fx!=fy)    {        father[fx]=fy;    }}//处理最大生成树后的边的关系struct edge{    edge *next;    int t,d;    edge()    {        next=NULL;    }}*head[MAXN];void Add(int s,int t,int d){    edge *p=new(edge);    p->t=t,p->d=d,p->next=head[s];    head[s]=p;}void AddEdge(int s,int t,int d){    Add(s,t,d);    Add(t,s,d);}//一个dfs过程，对于和v在一棵树上的所有结点计算其在树中的高度以及up[i][0]和Min[i][0]void BuildTree(int v){    visit[v]=true;    for(edge *p=head[v]; p; p=p->next)    {        if(!visit[p->t])        {            up[p->t][0]=v;            Min[p->t][0]=p->d;            h[p->t]=h[v]+1;            BuildTree(p->t);        }    }}//得到u和v两分支高度相同的节点，在此基础上开始倍增int Move(int &v,int H){    int rec = inf;    for(int i=MAXD-1; i>=0; i--)    {        if(h[up[v][i]]>=H)        {            rec=min(rec,Min[v][i]);            v=up[v][i];        }    }    return rec;}//倍增算法实现询问u和v路径上最小值int Query(int u,int v){    if(Find(u)!=Find(v))return -1;    int rec = inf;    if(h[u]!=h[v])rec=h[u]>h[v]?Move(u,h[v]):Move(v,h[u]);    if(u==v) return rec;    for(int i=MAXD-1; i>=0; i--)    {        if(up[u][i]!=up[v][i])        {            rec=min(rec,min(Min[u][i],Min[v][i]));            u=up[u][i];            v=up[v][i];        }    }    rec=min(rec,min(Min[u][0],Min[v][0]));    return rec;}int main(){     //输入   //freopen("truck.in", "r", stdin);    //freopen("truck.out", "w", stdout);    memset(head,0,sizeof(head));    memset(up,0,sizeof(up));    scanf("%d %d",&n,&m);    for(int i=0; i<m; i++)scanf("%d %d %d",&e[i].s,&e[i].t,&e[i].d);        //排序后生产最大生成树构成的森林    sort(e,e+m,cmp);    init();    for(int i=0; i<m; i++)    {        if(Find(e[i].s)!=Find(e[i].t))        {            Union(e[i].s,e[i].t);            AddEdge(e[i].s,e[i].t,e[i].d);        }    }        //初始化每一个结点的up[i][0]和Min[i][0],并计算结点在树中高度    memset(visit,false,sizeof(visit));    for(int i=1; i<=n; i++)    {        if(!visit[i])        {            h[i]=0;            BuildTree(i);            Min[i][0]=inf;            up[i][0]=i;        }    }        //预处理出up[i][j]和Min[i][j]数组    for(int i=1; i<MAXD; i++)    {        for(int j=1; j<=n; j++)        {            up[j][i]=up[up[j][i-1]][i-1];            Min[j][i]=min(Min[j][i-1],Min[up[j][i-1]][i-1]);        }    }        //处理询问    scanf("%d",&q);    while(q--)    {        int u,v;        scanf("%d %d",&u,&v);        printf("%d\n",Query(u,v));    }    return 0;}

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