题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=2874

这题有不连通的情况，特别注意。

觉得是存query的姿势不对，用前向星存了一遍，还是T……

 /*

 ━━━━━┒ギリギリ♂ eye！

 ┓┏┓┏┓┃キリキリ♂ mind！

 ┛┗┛┗┛┃＼○／

 ┓┏┓┏┓┃ /

 ┛┗┛┗┛┃ノ)

 ┓┏┓┏┓┃

 ┛┗┛┗┛┃

 ┓┏┓┏┓┃

 ┛┗┛┗┛┃

 ┓┏┓┏┓┃

 ┛┗┛┗┛┃

 ┓┏┓┏┓┃

 ┃┃┃┃┃┃

 ┻┻┻┻┻┻

 */

 #include <algorithm>

 #include <iostream>

 #include <iomanip>

 #include <cstring>

 #include <climits>

 #include <complex>

 #include <fstream>

 #include <cassert>

 #include <cstdio>

 #include <bitset>

 #include <vector>

 #include <deque>

 #include <queue>

 #include <stack>

 #include <ctime>

 #include <set>

 #include <map>

 #include <cmath>

 using namespace std;

 #define fr first

 #define sc second

 #define cl clear

 #define BUG puts("here!!!")

 #define W(a) while(a--)

 #define pb(a) push_back(a)

 #define Rint(a) scanf("%d", &a)

 #define Rll(a) scanf("%lld", &a)

 #define Rs(a) scanf("%s", a)

 #define Cin(a) cin >> a

 #define FRead() freopen("in", "r", stdin)

 #define FWrite() freopen("out", "w", stdout)

 #define Rep(i, len) for(int i = 0; i < (len); i++)

 #define For(i, a, len) for(int i = (a); i < (len); i++)

 #define Cls(a) memset((a), 0, sizeof(a))

 #define Clr(a, x) memset((a), (x), sizeof(a))

 #define Full(a) memset((a), 0x7f7f, sizeof(a))

 #define lp p << 1

 #define rp p << 1 | 1

 #define pi 3.14159265359

 #define RT return

 #define lowbit(x) x & (-x)

 #define onenum(x) __builtin_popcount(x)

 typedef long long LL;

 typedef long double LD;

 typedef unsigned long long ULL;

 typedef pair<int, int> pii;

 typedef pair<string, int> psi;

 typedef map<string, int> msi;

 typedef vector<int> vi;

 typedef vector<LL> vl;

 typedef vector<vl> vvl;

 typedef vector<bool> vb;

 typedef struct Query {

     int idx;

     int u, v;

     Query() {}

     Query(int uu, int vv, int ii) : u(uu), v(vv), idx(ii) {}

 }Query;

 typedef struct Edge {

     int u, v, w, idx;

     int next;

     Edge() {}

     Edge(int uu, int vv, int ww) : u(uu), v(vv), w(ww) {}

 }Edge;

 typedef struct Ans {

     int idx;

     int ans;

     Ans() {}

     Ans(int aa, int ii) :ans(aa), idx(ii) {}

 }Ans;

 const int maxn = ;

 const int maxm = ;

 int n, m, c, qcnt;

 int depth[maxn];

 bool vis[maxn];

 int pre[maxn];

 Ans ans[maxm];

 Edge edge[maxn];

 Edge q[maxm];

 Query qq[maxm];

 int qhead[maxm];

 int head[maxn];

 int ecnt;

 int u, v, w;

 void adde(int u, int v, int w) {

     edge[ecnt].u = u;

     edge[ecnt].v = v;

     edge[ecnt].w = w;

     edge[ecnt].next = head[u];

     head[u] = ecnt++;

 }

 void addq(int u, int v, int i) {

     q[qcnt].u = u;

     q[qcnt].v = v;

     q[qcnt].idx = i;

     q[qcnt].next = qhead[u];

     qhead[u] = ecnt++;

 }

 int find(int x) {

     return x == pre[x] ? x : pre[x] = find(pre[x]);

 }

 void unite(int x, int y) {

     x = find(x);

     y = find(y);

     if(x != y) pre[y] = x;

 }

 void dfs(int u, int p, int d) {

     depth[u] = d;

     for(int i = head[u]; ~i; i=edge[i].next) {

         int v = edge[i].v;

         if(!vis[v] && v != p) {

             dfs(v, u, d+edge[i].w);

             unite(u, v);

         }

     }

     vis[u] = ;

     for(int i = qhead[u]; ~i; i=q[i].next) {

         int uu = q[i].u;

         int vv = q[i].v;

         int idx = q[i].idx;

         if((vis[vv] && uu == u) || (vis[uu] && vv == u)) {

             ans[idx].ans = depth[vv] + depth[uu];

         }

     }

 }

 bool cmp(Ans x, Ans y) {

     return x.idx < y.idx;

 }

 int ufs[maxn];

 int find1(int x) {

     return ufs[x] == x ? x : ufs[x] = find1(ufs[x]);

 }

 void unite1(int x, int y) {

     x = find1(x);

     y = find1(y);

     if(x != y) ufs[y] = x;

 }

 inline bool scan_d(int &num) {

     char in;bool IsN=false;

     in=getchar();

     if(in==EOF) return false;

     while(in!='-'&&(in<''||in>'')) in=getchar();

     if(in=='-'){ IsN=true;num=;}

     else num=in-'';

     while(in=getchar(),in>=''&&in<=''){

             num*=,num+=in-'';

     }

     if(IsN) num=-num;

     return true;

 }

 int main() {

     // FRead();

     while(~scanf("%d%d%d",&n,&m,&c)) {

         Cls(vis); Cls(depth); Cls(ans); Clr(head, -); Clr(qhead, -);

         qcnt = ; Rep(i, n+) pre[i] = i, ufs[i] = i;

         Rep(i, m) {

             scan_d(u); scan_d(v); scan_d(w);

             adde(u, v, w); adde(v, u, w);

             unite1(u, v);

         }

         Rep(i, c) {

             scan_d(u); scan_d(v);

             addq(u, v, i);

             qq[i] = Query(u, v, i);

         }

         For(i, , n+) if(!vis[i]) dfs(i, -, );

         Rep(i, c) {

             if(find1(qq[ans[i].idx].u) != find1(qq[ans[i].idx].v)) puts("Not connected");

             else printf("%d\n", ans[i].ans);

         }

     }

     RT ;

 }

……TARJAN也T了……

 /*

 ━━━━━┒ギリギリ♂ eye！

 ┓┏┓┏┓┃キリキリ♂ mind！

 ┛┗┛┗┛┃＼○／

 ┓┏┓┏┓┃ /

 ┛┗┛┗┛┃ノ)

 ┓┏┓┏┓┃

 ┛┗┛┗┛┃

 ┓┏┓┏┓┃

 ┛┗┛┗┛┃

 ┓┏┓┏┓┃

 ┛┗┛┗┛┃

 ┓┏┓┏┓┃

 ┃┃┃┃┃┃

 ┻┻┻┻┻┻

 */

 #include <algorithm>

 #include <iostream>

 #include <iomanip>

 #include <cstring>

 #include <climits>

 #include <complex>

 #include <fstream>

 #include <cassert>

 #include <cstdio>

 #include <bitset>

 #include <vector>

 #include <deque>

 #include <queue>

 #include <stack>

 #include <ctime>

 #include <set>

 #include <map>

 #include <cmath>

 using namespace std;

 #define fr first

 #define sc second

 #define cl clear

 #define BUG puts("here!!!")

 #define W(a) while(a--)

 #define pb(a) push_back(a)

 #define Rint(a) scanf("%d", &a)

 #define Rll(a) scanf("%lld", &a)

 #define Rs(a) scanf("%s", a)

 #define Cin(a) cin >> a

 #define FRead() freopen("in", "r", stdin)

 #define FWrite() freopen("out", "w", stdout)

 #define Rep(i, len) for(int i = 0; i < (len); i++)

 #define For(i, a, len) for(int i = (a); i < (len); i++)

 #define Cls(a) memset((a), 0, sizeof(a))

 #define Clr(a, x) memset((a), (x), sizeof(a))

 #define Full(a) memset((a), 0x7f7f, sizeof(a))

 #define lp p << 1

 #define rp p << 1 | 1

 #define pi 3.14159265359

 #define RT return

 #define lowbit(x) x & (-x)

 #define onenum(x) __builtin_popcount(x)

 typedef long long LL;

 typedef long double LD;

 typedef unsigned long long ULL;

 typedef pair<int, int> pii;

 typedef pair<string, int> psi;

 typedef map<string, int> msi;

 typedef vector<int> vi;

 typedef vector<LL> vl;

 typedef vector<vl> vvl;

 typedef vector<bool> vb;

 typedef struct Query {

     int idx;

     int u, v;

     Query() {}

     Query(int uu, int vv, int ii) : u(uu), v(vv), idx(ii) {}

 }Query;

 typedef struct Edge {

     int u, v, w;

     int next;

     Edge() {}

     Edge(int uu, int vv, int ww) : u(uu), v(vv), w(ww) {}

 }Edge;

 typedef struct Ans {

     int idx;

     int ans;

     Ans() {}

     Ans(int aa, int ii) :ans(aa), idx(ii) {}

 }Ans;

 const int maxn = ;

 const int maxm = ;

 int n, m, c, qcnt;

 int depth[maxn];

 bool vis[maxn];

 int pre[maxn];

 Query q[maxm];

 Ans ans[maxm];

 Edge edge[maxn];

 int head[maxn];

 int ecnt;

 int u, v, w;

 void adde(int u, int v, int w) {

     edge[ecnt].u = u;

     edge[ecnt].v = v;

     edge[ecnt].w = w;

     edge[ecnt].next = head[u];

     head[u] = ecnt++;

 }

 int find(int x) {

     return x == pre[x] ? x : pre[x] = find(pre[x]);

 }

 void unite(int x, int y) {

     x = find(x);

     y = find(y);

     if(x != y) pre[y] = x;

 }

 void dfs(int u, int p, int d) {

     depth[u] = d;

     for(int i = head[u]; ~i; i=edge[i].next) {

         int v = edge[i].v;

         if(!vis[v] && v != p) {

             dfs(v, u, d+edge[i].w);

             unite(u, v);

         }

     }

     vis[u] = ;

     Rep(i, qcnt) {

         int uu = q[i].u;

         int vv = q[i].v;

         int idx = q[i].idx;

         if((vis[vv] && uu == u) || (vis[uu] && vv == u)) {

             ans[idx].idx = idx;

             ans[idx].ans = depth[vv] + depth[uu];

         }

     }

 }

 bool cmp(Ans x, Ans y) {

     return x.idx < y.idx;

 }

 int ufs[maxn];

 int find1(int x) {

     return ufs[x] == x ? x : ufs[x] = find1(ufs[x]);

 }

 void unite1(int x, int y) {

     x = find1(x);

     y = find1(y);

     if(x != y) ufs[y] = x;

 }

 inline bool scan_d(int &num) {

     char in;bool IsN=false;

     in=getchar();

     if(in==EOF) return false;

     while(in!='-'&&(in<''||in>'')) in=getchar();

     if(in=='-'){ IsN=true;num=;}

     else num=in-'';

     while(in=getchar(),in>=''&&in<=''){

             num*=,num+=in-'';

     }

     if(IsN) num=-num;

     return true;

 }

 int main() {

     // FRead();

     while(~scanf("%d%d%d",&n,&m,&c)) {

         Cls(vis); Cls(depth); Cls(ans); Clr(head, -);

         qcnt = ; Rep(i, n+) pre[i] = i, ufs[i] = i;

         Rep(i, m) {

             scan_d(u); scan_d(v); scan_d(w);

             adde(u, v, w); adde(v, u, w);

             unite1(u, v);

         }

         Rep(i, c) {

             scan_d(u); scan_d(v);

             q[qcnt++] = Query(u, v, i);

         }

         For(i, , n+) if(!vis[i]) dfs(i, -, );

         Rep(i, c) {

             if(find1(q[ans[i].idx].u) != find1(q[ans[i].idx].v)) puts("Not connected");

             else printf("%d\n", ans[i].ans);

         }

     }

     RT ;

 }

在线胡搞T了，等下写个离线的。

TLE代码：

 /*

 ━━━━━┒ギリギリ♂ eye！

 ┓┏┓┏┓┃キリキリ♂ mind！

 ┛┗┛┗┛┃＼○／

 ┓┏┓┏┓┃ /

 ┛┗┛┗┛┃ノ)

 ┓┏┓┏┓┃

 ┛┗┛┗┛┃

 ┓┏┓┏┓┃

 ┛┗┛┗┛┃

 ┓┏┓┏┓┃

 ┛┗┛┗┛┃

 ┓┏┓┏┓┃

 ┃┃┃┃┃┃

 ┻┻┻┻┻┻

 */

 #include <algorithm>

 #include <iostream>

 #include <iomanip>

 #include <cstring>

 #include <climits>

 #include <complex>

 #include <fstream>

 #include <cassert>

 #include <cstdio>

 #include <bitset>

 #include <vector>

 #include <deque>

 #include <queue>

 #include <stack>

 #include <ctime>

 #include <set>

 #include <map>

 #include <cmath>

 using namespace std;

 #define fr first

 #define sc second

 #define cl clear

 #define BUG puts("here!!!")

 #define W(a) while(a--)

 #define pb(a) push_back(a)

 #define Rint(a) scanf("%d", &a)

 #define Rll(a) scanf("%I64d", &a)

 #define Rs(a) scanf("%s", a)

 #define Cin(a) cin >> a

 #define FRead() freopen("in", "r", stdin)

 #define FWrite() freopen("out", "w", stdout)

 #define Rep(i, len) for(int i = 0; i < (len); i++)

 #define For(i, a, len) for(int i = (a); i < (len); i++)

 #define Cls(a) memset((a), 0, sizeof(a))

 #define Clr(a, x) memset((a), (x), sizeof(a))

 #define Full(a) memset((a), 0x7f7f, sizeof(a))

 #define pi 3.14159265359

 #define RT return

 #define lowbit(x) x & (-x)

 #define onenum(x) __builtin_popcount(x)

 typedef long long LL;

 typedef long double LD;

 typedef unsigned long long ULL;

 typedef pair<int, int> pii;

 typedef pair<string, int> psi;

 typedef map<string, int> msi;

 typedef vector<int> vi;

 typedef vector<LL> vl;

 typedef vector<vl> vvl;

 typedef vector<bool> vb;

 typedef struct Edge {

     int u, v, w;

     int next;

 }Edge;

 const int maxn = ;

 const int maxm = ;

 int n, m, c;

 int depth[maxn], fa[maxn];

 int pre[maxn];

 Edge edge[maxm];

 int head[maxn];

 int ecnt;

 bool vis[maxn];

 void adde(int u, int v, int w) {

     edge[ecnt].u = u;

     edge[ecnt].v = v;

     edge[ecnt].w = w;

     edge[ecnt].next = head[u];

     head[u] = ecnt++;

 }

 int find(int x) {

     x == pre[x] ? x : pre[x] = find(pre[x]);

 }

 void unite(int x, int y) {

     x = find(x);

     y = find(y);

     if(x != y) pre[y] = x;

 }

 void dfs(int u, int p, int d) {

     vis[u] = ;

     depth[u] = d; fa[u] = p;

     for(int i = head[u]; ~i; i=edge[i].next) {

         int v = edge[i].v;

         int w = edge[i].w;

         if(!vis[v]) dfs(v, u, d+w);

     }

 }

 int lca(int u, int v) {

     int s = ;

     while(depth[u] > depth[v]) {

         s += depth[u];

         u = pre[u];

     }

     while(depth[v] > depth[u]) {

         s += depth[v];

         v = pre[v];

     }

     while(u != v) {

         s += (depth[u] + depth[v]);

         u = pre[u];

         v = pre[v];

     }

     return s;

 }

 inline bool scan_d(int &num) {

     char in;bool IsN=false;

     in=getchar();

     if(in==EOF) return false;

     while(in!='-'&&(in<''||in>'')) in=getchar();

     if(in=='-'){ IsN=true;num=;}

     else num=in-'';

     while(in=getchar(),in>=''&&in<=''){

             num*=,num+=in-'';

     }

     if(IsN) num=-num;

     return true;

 }

 int main() {

     FRead();

     int u, v, w;

     while(~scanf("%d%d%d",&n,&m,&c)) {

         Clr(head, -); ecnt = ;

         Rep(i, n+) pre[i] = i;

         Rep(i, m) {

             scan_d(u); scan_d(v); scan_d(w);

             adde(u, v, w); adde(v, u, w);

             unite(u, v);

         }

         For(i, , n+) {

             if(!vis[i]) {

                 dfs(i, -, );

             }

         }

         W(c) {

             scan_d(u); scan_d(v);

             if(find(u) != find(v)) puts("Not connected");

             else printf("%d\n", lca(u, v));

         }

     }

     RT ;

 }

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