HDU 4738——Caocao's Bridges——————【求割边/桥的最小权值】

#include<stdio.h>
#include<algorithm>
#include<string.h>
#include<queue>
#include<vector>
using namespace std;
const int maxn = 1010;
const int INF = 0x3f3f3f3f;
struct Edge{
    int from,to,dist,next;
    Edge(){}
    Edge(int _to,int _next,int _dist):to(_to),next(_next),dist(_dist){}
}edges[maxn*maxn*2];
int tot , head[maxn];
int dfn[maxn], bridge[maxn], dfs_clock, low[maxn], brinum;
int Mins;
void init(){
    tot = 0;
    dfs_clock = 0;
    brinum = 0;
    Mins = INF;
    memset(head,-1,sizeof(head));
    memset(dfn,0,sizeof(dfn));
    memset(bridge,0,sizeof(bridge));
}
void AddEdge(int _u,int _v,int _w){
    edges[tot] = Edge(_v,head[_u],_w);
    head[_u] = tot++;
}
int dfs(int u,int fa){
    int lowu = dfn[u] = ++dfs_clock;
    for(int i = head[u]; i != -1; i = edges[i].next){
        int v = edges[i].to;
        if(!dfn[v]){
            int lowv = dfs(v,i);
            lowu = min(lowu,lowv);
            if(lowv > dfn[u]){
                bridge[v] = 1;
                brinum++;
                Mins = min(Mins , edges[i].dist);
            }
        }else if(dfn[v] < dfn[u] && (fa^1) != i){
            lowu = min(dfn[v],lowu);
        }
    }
    low[u] = lowu;
    return lowu;
}
int main(){
    int n,m;
    while(scanf("%d%d",&n,&m)!=EOF&&(n+m)){
        int a,b,c;
        init();
        for(int i = 0; i <m ;i++){
            scanf("%d%d%d",&a,&b,&c);
            AddEdge(a,b,c);
            AddEdge(b,a,c);
        }
        int times = 0;
        for(int i = 1; i <= n; i++){
            if(!dfn[i]){
                times++;
                dfs(i,-1);
            }
        }
        if(times > 1){
            puts("0");
            continue;
        }
        if(brinum == 0){
            puts("-1");
            continue;
        }
        printf("%d\n",Mins == 0? 1:Mins);
    }
    return 0;
}