題目：還是自己看題目吧

trick：當不連通時不需要人去炸。否則，當橋的費用為0時當然需要一個人去炸。。。

#include <set> #include <map> #include <list> #include <cmath> #include <queue> #include <stack> #include <string> #include <vector> #include <cstdio> #include <cstring> #include <iostream> #include <algorithm>using namespace std;typedef long long ll; typedef unsigned long long ull;#define debug puts("here") #define rep(i,n) for(int i=0;i<n;i++) #define rep1(i,n) for(int i=1;i<=n;i++) #define REP(i,a,b) for(int i=a;i<=b;i++) #define foreach(i,vec) for(unsigned i=0;i<vec.size();i++) #define pb push_back #define RD(n) scanf("%d",&n) #define RD2(x,y) scanf("%d%d",&x,&y) #define RD3(x,y,z) scanf("%d%d%d",&x,&y,&z) #define RD4(x,y,z,w) scanf("%d%d%d%d",&x,&y,&z,&w) #define All(vec) vec.begin(),vec.end() #define MP make_pair #define PII pair<int,int> #define PQ priority_queue #define cmax(x,y) x = max(x,y) #define cmin(x,y) x = min(x,y) #define Clear(x) memset(x,0,sizeof(x)) /*#pragma comment(linker, "/STACK:1024000000,1024000000")int size = 256 << 20; // 256MB char *p = (char*)malloc(size) + size; __asm__("movl %0, %%esp\n" :: "r"(p) );*/char IN; bool NEG; inline void Int(int &x){NEG = 0;while(!isdigit(IN=getchar()))if(IN=='-')NEG = 1;x = IN-'0';while(isdigit(IN=getchar()))x = x*10+IN-'0';if(NEG)x = -x; } inline void LL(ll &x){NEG = 0;while(!isdigit(IN=getchar()))if(IN=='-')NEG = 1;x = IN-'0';while(isdigit(IN=getchar()))x = x*10+IN-'0';if(NEG)x = -x; }/******** program ********************/const int MAXN = 1005; const int INF = 1e9;int low[MAXN],dfn[MAXN],dep; int po[MAXN],tol; int best;struct Edge{int y,cost,id,next; }edge[MAXN*MAXN<<1];void add(int x,int y,int cost,int id){edge[++tol].y = y;edge[tol].cost = cost;edge[tol].id = id;edge[tol].next = po[x];po[x] = tol; }void dfs(int x,int fid){dfn[x] = low[x] = ++ dep;for(int i=po[x];i;i=edge[i].next){int y = edge[i].y;int id = edge[i].id;if(id==fid)continue;if(!dfn[y]){dfs(y,id);cmin(low[x],low[y]);if(low[y]>dfn[x]){if(edge[i].cost<best)best = edge[i].cost;}}else cmin(low[x],dfn[y]);} }int main(){#ifndef ONLINE_JUDGEfreopen("sum.in","r",stdin);//freopen("sum.out","w",stdout); #endifint size = 256 << 20; // 256MBchar *p = (char*)malloc(size) + size;__asm__("movl %0, %%esp\n" :: "r"(p) );int n,m,x,y,cost;while(RD2(n,m),n||m){Clear(po);tol = 0;rep1(i,m){RD3(x,y,cost);if(x>n||y>n)continue;add(x,y,cost,i);add(y,x,cost,i);}dep = 0;Clear(dfn);best = INF;int ok = 0;rep1(i,n)if(!dfn[i]){ok ++;dfs(i,0);}if(best==0)best = 1;if(ok>1)best = 0;printf("%d\n",best==INF?-1:best);}return 0; }

　　

轉載于:https://www.cnblogs.com/yejinru/p/3323114.html

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