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#tree #distance #linker #each #struct #output

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A weighted tree is given. You must find the distance between two given nodes.

Input

The first line contains the number of nodes of the tree n (1 ≤ n ≤ 50000). The nodes are numbered from 0 to n – 1.Each of the next n – 1 lines contains three integers u, v, w, which correspond to an edgewith weight w (0 ≤ w ≤ 1000) connecting nodes u and v.The next line contains the number of queries m (1 ≤ m ≤ 75000).In each of the next m lines there are two integers.

Output

For each query, output the distance between the nodes with the given numbers.

Sample

input	output
3 1 0 1 2 0 1 3 0 1 0 2 1 2	1 1 2

LCA向RMQ转换，注意询问时要判断区间下界是否小于上界，并且记录深度时不能带权。
Accode：

#pragma comment(linker, "/STACK:0x10000000")
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <string>
#define RMQ_min(a, b) (D[a] < D[b] ? (a) : (b))
const int maxN = 50010;
const int maxORD = 100010;
struct Edge {int v, d; Edge *next;};
Edge *edge[maxN];
int D[maxORD], ord[maxORD], f[maxORD][20];
int fir[maxN], dist[maxN], Ind;

void Dfs(int u, int Last, int Dep)
{
    ord[++Ind] = u; fir[u] = Ind; D[Ind] = Dep;
    for (Edge *p = edge[u]; p; p = p -> next)
    if (p -> v - Last)
    {
        dist[p -> v] = dist[u] + p -> d;
        Dfs(p -> v, u, Dep + 1);
        ord[++Ind] = u;
        D[Ind] = Dep;
    }
    return;
}

inline void RMQ_set()
{
    for (int i = 1; i < Ind + 1; ++i) f[i][0] = i;
    for (int q = 0; 1 << q < Ind; ++q)
    for (int i = 1; i + (1 << q) < Ind + 1; ++i)
        f[i][q + 1] = RMQ_min(f[i][q], f[i + (1 << q)][q]);
    return;
}

inline int RMQ(int L, int R)
{
    if (L == R) return L;
    if (L > R) std::swap(L, R); //
    int q = 0; for (; 1 << q < R - L + 2; ++q); --q;
    return RMQ_min(f[L][q], f[R - (1 << q) + 1][q]);
}

inline int getint()
{
    int res = 0; char tmp;
    while (!isdigit(tmp = getchar()));
    do res = (res << 3) + (res << 1) + tmp - '0';
    while (isdigit(tmp = getchar()));
    return res;
}

inline void Ins(int u, int v, int d)
{
    Edge *p = new Edge; p -> v = v;
    p -> d = d; p -> next = edge[u];
    edge[u] = p; return;
}

int main()
{
    freopen("tree.in", "r", stdin);
    freopen("tree.out", "w", stdout);
    for (int n = getint(); --n;)
    {
        int u = getint(), v = getint(), d = getint();
        Ins(u, v, d); Ins(v, u, d);
    }
    Dfs(0, -1, 0); RMQ_set();
    for (int m = getint(); m; --m)
    {
        int u = getint(), v = getint();
        printf("%d\n", dist[u] + dist[v] -
               (dist[ord[RMQ(fir[u], fir[v])]] << 1));
    }
    return 0;
}

#undef RMQ_min