题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=2586
这题以前做过…现在用tarjan搞一发…竟然比以前暴力过的慢…………
由于是离线算法，需要Query来保存查询数据，Ans来保存结果。最后输出的时候按照idx的顺序输出，所以胡搞了个排序。。
dfs每次更新depth，当前点depth是上一个点累积下来的。
1 /* 2 ━━━━━┒ギリギリ♂ eye！ 3 ┓┏┓┏┓┃キリキリ♂ mind！ 4 ┛┗┛┗┛┃＼○／ 5 ┓┏┓┏┓┃ / 6 ┛┗┛┗┛┃ノ) 7 ┓┏┓┏┓┃ 8 ┛┗┛┗┛┃ 9 ┓┏┓┏┓┃ 10 ┛┗┛┗┛┃ 11 ┓┏┓┏┓┃ 12 ┛┗┛┗┛┃ 13 ┓┏┓┏┓┃ 14 ┃┃┃┃┃┃ 15 ┻┻┻┻┻┻ 16 */ 17 #include <algorithm> 18 #include <iostream> 19 #include <iomanip> 20 #include <cstring> 21 #include <climits> 22 #include <complex> 23 #include <fstream> 24 #include <cassert> 25 #include <cstdio> 26 #include <bitset> 27 #include <vector> 28 #include <deque> 29 #include <queue> 30 #include <stack> 31 #include <ctime> 32 #include <set> 33 #include <map> 34 #include <cmath> 35 36 using namespace std; 37 38 #define fr first 39 #define sc second 40 #define cl clear 41 #define BUG puts("here!!!") 42 #define W(a) while(a--) 43 #define pb(a) push_back(a) 44 #define Rint(a) scanf("%d", &a) 45 #define Rll(a) scanf("%lld", &a) 46 #define Rs(a) scanf("%s", a) 47 #define Cin(a) cin >> a 48 #define FRead() freopen("in", "r", stdin) 49 #define FWrite() freopen("out", "w", stdout) 50 #define Rep(i, len) for(int i = 0; i < (len); i++) 51 #define For(i, a, len) for(int i = (a); i < (len); i++) 52 #define Cls(a) memset((a), 0, sizeof(a)) 53 #define Clr(a, x) memset((a), (x), sizeof(a)) 54 #define Full(a) memset((a), 0x7f7f, sizeof(a)) 55 #define lrt rt << 1 56 #define rrt rt << 1 | 1 57 #define pi 3.14159265359 58 #define RT return 59 typedef long long LL; 60 typedef long double LD; 61 typedef unsigned long long ULL; 62 typedef pair<int, int> pii; 63 typedef pair<string, int> psi; 64 typedef map<string, int> msi; 65 typedef vector<LL> vl; 66 typedef vector<vl> vvl; 67 typedef vector<bool> vb; 68 69 typedef struct Query { 70 int idx; 71 int u, v; 72 Query() {} 73 Query(int uu, int vv, int ii) : u(uu), v(vv), idx(ii) {} 74 }Query; 75 76 typedef struct Edge { 77 int v, w; 78 Edge() {} 79 Edge(int vv, int ww) : v(vv), w(ww) {} 80 }Edge; 81 82 typedef struct Ans { 83 int idx; 84 int ans; 85 Ans() {} 86 Ans(int aa, int ii) :ans(aa), idx(ii) {} 87 }Ans; 88 89 const int maxn = 40010; 90 const int maxm = 222; 91 int n, m, qcnt, acnt; 92 int depth[maxn]; 93 int in[maxn]; 94 bool vis[maxn]; 95 int pre[maxn]; 96 Query q[maxm]; 97 Ans ans[maxn]; 98 vector<Edge> G[maxn]; 99 int u, v, w; 100 101 int find(int x) { 102 return x == pre[x] ? x : pre[x] = find(pre[x]); 103 } 104 105 void unite(int x, int y) { 106 x = find(x); 107 y = find(y); 108 if(x != y) pre[y] = x; 109 } 110 111 void dfs(int u, int d) { 112 // pre[u] = u; 113 depth[u] = d; 114 Rep(i, G[u].size()) { 115 int v = G[u][i].v; 116 if(!vis[v]) { 117 dfs(v, d+G[u][i].w); 118 unite(u, v); 119 } 120 } 121 vis[u] = 1; 122 Rep(i, qcnt) { 123 int uu = q[i].u; 124 int vv = q[i].v; 125 int idx = q[i].idx; 126 if(vis[uu] && vv == u) { 127 ans[acnt].idx = idx; 128 ans[acnt++].ans = abs(depth[vv] - depth[uu]); 129 } 130 if(vis[vv] && uu == u) { 131 ans[acnt].idx = idx; 132 ans[acnt++].ans = abs(depth[uu] - depth[vv]); 133 } 134 } 135 } 136 137 bool cmp(Ans x, Ans y) { 138 return x.idx < y.idx; 139 } 140 141 int main() { 142 // FRead(); 143 int T; 144 Rint(T); 145 W(T) { 146 Rint(n); Rint(m); 147 Cls(vis); Cls(depth); Cls(ans); Cls(G); 148 acnt = qcnt = 0; Rep(i, n+5) G[i].cl(), pre[i] = i; 149 Rep(i, n-1) { 150 Rint(u); Rint(v); Rint(w); 151 G[u].push_back(Edge(v, w)); 152 in[v]++; 153 } 154 Rep(i, m) { 155 Rint(u); Rint(v); 156 q[qcnt++] = Query(u, v, i); 157 } 158 For(i, 1, n+1) if(in[i] == 0) dfs(i, 0); 159 sort(ans, ans+acnt, cmp); 160 Rep(i, acnt) { 161 printf("%d ", ans[i].ans); 162 } 163 } 164 RT 0; 165 }