http://acm.hdu.edu.cn/showproblem.php?pid=2874
给出一个森林，询问任意两点最短距离。
tarjan跑一遍即可，就是这个题卡内存，vector会MLE，换前向星就好了。
1 #include<iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<map> 5 #include<set> 6 #include<stack> 7 #include<deque> 8 #include<bitset> 9 #include<unordered_map> 10 #include<unordered_set> 11 #include<queue> 12 #include<cstdlib> 13 #include<ctype.h> 14 #include<ctime> 15 #include<functional> 16 #include<algorithm> 17 #include<bits/stdc++.h> 18 using namespace std; 19 #define LL long long 20 #define pii pair<int,int> 21 #define mp make_pair 22 #define pb push_back 23 #define fi first 24 #define se second 25 #define inf 0x3f3f3f3f 26 #define debug puts("debug") 27 #define mid ((L+R)>>1) 28 #define lc (id<<1) 29 #define rc (id<<1|1) 30 const int maxn=10010; 31 const int maxm=50050; 32 const double PI=acos(-1.0); 33 const double eps=1e-6; 34 const LL mod=1e9+7; 35 LL gcd(LL a,LL b){return b==0?a:gcd(b,a%b);} 36 LL lcm(LL a,LL b){return a/gcd(a,b)*b;} 37 LL qpow(LL a,LL b,LL c){LL r=1; for(;b;b>>=1,a=a*a%c)if(b&1)r=r*a%c;return r;} 38 template<class T> 39 void prt(T v){for(auto x:v)cout<<x<<' ';cout<<endl;} 40 struct Edge{int v,w,next;}e,e1[20020],e2[2000020]; 41 int first1[maxn],first2[maxn],tot1,tot2; 42 void add1(int u,int v,int w){ 43 e1[tot1].v=v; 44 e1[tot1].w=w; 45 e1[tot1].next=first1[u]; 46 first1[u]=tot1++; 47 } 48 void add2(int u,int v,int w){ 49 e2[tot2].v=v; 50 e2[tot2].w=w; 51 e2[tot2].next=first2[u]; 52 first2[u]=tot2++; 53 } 54 55 bool vis[maxn]; 56 int f[maxn],d[maxn],ans[1000010]; 57 int getf(int u){return f[u]==u?u:f[u]=getf(f[u]);} 58 void tarjan(int u){ 59 vis[u]=1; 60 for(int i=first1[u];~i;i=e1[i].next){ 61 e=e1[i]; 62 int v=e.v,w=e.w; 63 if(!vis[v]){ 64 d[v]=d[u]+w; 65 tarjan(v); 66 f[v]=u; 67 } 68 } 69 for(int i=first2[u];~i;i=e2[i].next){ 70 e=e2[i]; 71 int v=e.v,id=e.w; 72 if(vis[v]){ 73 ans[id]=d[u]+d[v]-2*d[getf(v)]; 74 } 75 } 76 } 77 void read(int &n){ 78 n=0; char c=getchar(); 79 while(c<'0'||c>'9')c=getchar(); 80 while(c>='0'&&c<='9') n=(n<<3)+(n<<1)+c-'0',c=getchar(); 81 } 82 int main(){ 83 int t,n,m,i,j,u,v,w; 84 while(~scanf("%d%d%d",&n,&m,&t)){ 85 for(i=1;i<=n;++i)f[i]=i; 86 tot1=tot2=0; 87 memset(first1,-1,sizeof(first1)); 88 memset(first2,-1,sizeof(first2)); 89 while(m--){ 90 //scanf("%d%d%d",&u,&v,&w); 91 read(u),read(v),read(w); 92 add1(u,v,w); 93 add1(v,u,w); 94 } 95 for(i=1;i<=t;++i){ 96 ans[i]=-1; 97 //scanf("%d%d",&u,&v); 98 read(u),read(v); 99 add2(u,v,i); 100 add2(v,u,i); 101 } 102 memset(d,-1,sizeof(d)); 103 for(i=1;i<=n;++i){ 104 if(d[i]==-1) d[i]=0,memset(vis,0,sizeof(vis)),tarjan(i); 105 } 106 for(i=1;i<=t;++i){ 107 if(ans[i]==-1) puts("Not connected"); 108 else printf("%d ",ans[i]); 109 } 110 } 111 return 0; 112 }