比赛 中秋节快乐! 评测结果 AAAAAAAAAAAAAAAAAAAA
题目名称 货车运输 最终得分 100
用户昵称 wdsjl 运行时间 0.595 s
代码语言 C++ 内存使用 4.74 MiB
提交时间 2024-09-17 09:51:12
显示代码纯文本
#include <bits/stdc++.h>
using namespace std; 

const int MAXN = 10005;
const int INF =  999999999;

struct Edge1{  
    int x,y,dis;
}edge1[50005]; 

struct Edge2{
    int to,next,w;
}edge2[100005]; 

int cnt,n,m,head[MAXN],deep[MAXN],f[MAXN],fa[MAXN][21],w[MAXN][21];

bool vis[MAXN]; 

void addedge(int from, int to, int w){ 
    edge2[++cnt].next=head[from];
    edge2[cnt].to=to;
    edge2[cnt].w=w;
    head[from]=cnt;
    return ;
}

bool CMP(Edge1 x, Edge1 y){
    return x.dis>y.dis; 
}

int find(int x){  
    if(f[x]!=x) f[x]=find(f[x]);
    return f[x];
}

void kruskal(){
    sort(edge1+1, edge1+m+1, CMP); 
    for(int i=1; i<=n; i++)
        f[i]=i; 
    for(int i=1; i<=m; i++)
        if(find(edge1[i].x)!=find(edge1[i].y)){
            f[find(edge1[i].x)]=find(edge1[i].y);
            addedge(edge1[i].x, edge1[i].y, edge1[i].dis);
            addedge(edge1[i].y, edge1[i].x, edge1[i].dis); 
        }
    return ;
}

void dfs(int node){
    vis[node]=true;
    for(int i=head[node]; i; i=edge2[i].next){ 
        int to=edge2[i].to;
        if(vis[to]) continue;
        deep[to]=deep[node]+1; 
        fa[to][0]=node; 
        w[to][0]=edge2[i].w; 
        dfs(to);
    }
    return ;
}

int lca(int x, int y){
    if(find(x)!=find(y)) return -1; 
    int ans=INF;
    if(deep[x]>deep[y]) swap(x,y); 
    for(int i=20; i>=0; i--)
        if(deep[fa[y][i]]>=deep[x]){
            ans=min(ans, w[y][i]);  
            y=fa[y][i]; 
        }
    if(x==y) return ans; 
    for(int i=20; i>=0; i--)
        if(fa[x][i]!=fa[y][i]){
            ans=min(ans, min(w[x][i], w[y][i])); 
            x=fa[x][i]; 
            y=fa[y][i];
        }
    ans=min(ans, min(w[x][0], w[y][0]));
    return ans;
}

int main(){
	freopen("truck.in","r",stdin);
	freopen("truck.out","w",stdout); 
    int x,y,z,q;
    scanf("%d%d",&n,&m);
    for(int i=1; i<=m; i++){
        scanf("%d%d%d",&x,&y,&z);
        edge1[i].x=x;
        edge1[i].y=y;
        edge1[i].dis=z;
    } 
    kruskal();
    for(int i=1; i<=n; i++)
        if(!vis[i]){ 
            deep[i]=1; 
            dfs(i);
            fa[i][0]=i;
            w[i][0]=INF;
        }
    for(int i=1; i<=20; i++)
        for(int j=1; j<=n; j++){
            fa[j][i]=fa[fa[j][i-1]][i-1]; 
            w[j][i]=min(w[j][i-1], w[fa[j][i-1]][i-1]);
        }
    scanf("%d",&q);
    for(int i=1; i<=q; i++){
        scanf("%d%d",&x,&y);
        printf("%d\n",lca(x,y)); 
    }
    return 0;
}