hdu2586 LCA 离线算法

来源：互联网发布：天猫精灵知乎编辑：程序博客网时间：2024/05/18 18:20
大神的博客：http://blog.csdn.net/hnust_xiehonghao/article/details/9109295
#include <iostream>#include <string>#include <cstring>#include <cstdio>#include <cmath>#include <cstdlib>#include <algorithm>#include <queue>#include <map>#include <vector>#define MST(s,q) memset(s,q,sizeof(s))#define INF 0x3f3f3f3f#define MAXN 50005#define Lchild id<<1#define Rchild (id<<1)+1using namespace std;struct Query {    int v, no;} tmp;int N, M, T, F[MAXN], dis[MAXN], level[MAXN], vis[MAXN], ans[MAXN];vector<int>   node[MAXN], w[MAXN];vector<Query> query[MAXN];void init() {    for (int i = 0; i < MAXN; i++) {        F[i] = i;        ans[i] = dis[i] = vis[i] = 0;        level[i] = 1;        node[i].clear();        query[i].clear();        w[i].clear();    }}int Find (int x) {    if (F[x] == x) return x;    return F[x] = Find (F[x]);}void Union (int x, int y) {    int fa = Find (x), fb = Find (y);    if (fa == fb) return;    F[fb] = fa;}void LCA (int root, int value) {    vis[root] = 1;    dis[root] = value;    int len = node[root].size();    for (int i = 0; i < len; i++) {        int v = node[root][i];        if (vis[v]) continue;        LCA (v, value + w[root][i]); // 递归子树        Union (root, v);    }    len = query[root].size();    for (int i = 0; i < len; i++) {        int v = query[root][i].v, no = query[root][i].no;        if (!vis[v]) continue;        ans[no] = dis[root] + dis[v] - 2 * dis[Find (v)];    }}int main() {    cin >> T;    while (T--) {        cin >> N >> M;        init();        int u, v, z;        for (int i = 1; i < N; i++) {            scanf ("%d%d%d", &u, &v, &z);            node[u].push_back (v), w[u].push_back (z);            node[v].push_back (u), w[v].push_back (z);        }        for (int i = 0; i < M; i++) {            scanf ("%d%d", &u, &v);            tmp.no = i;            tmp.v = v, query[u].push_back (tmp);            tmp.v = u, query[v].push_back (tmp);        }        LCA (1, 0);        for (int i = 0; i < M; i++)            printf ("%d\n", ans[i]);    }}
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