poj2763 Housewife Wind--LCA转RMQ

原题链接：http://poj.org/problem?id=2763

题意：n个点，n-1条点的连线，数据保证任意两点可达，无环，接下来q行操作，两种形式，0 u 表示查询该人到u的时间；1 i w 表示第i条路的时间改为w。

分析：只能用RMQ来做，有点细节处理，都在注释里。

#define _CRT_SECURE_NO_DEPRECATE #include<iostream>#include<vector>#include<cstring>#include<queue>#include<stack>#include<algorithm>#include<cmath>#define INF 99999999#define eps 0.0001#define N ((1<<12)+10)using namespace std;struct Edge{int v;int index;int next;};int n, q, s;int index;int cnt;Edge edge[2 * 100005];int head[100005];int dis[100005];int father[100005];//父节点int time[100005];//第i条路的时间int node[2 * 100005];//保存第i次访问的节点int first[100005];//i这个节点是第几次访问到的int depth[2 * 100005];//第i次访问的节点的深度int dp[2 * 100005][25];//dp[i][j]表示从第i次访问开始，连续2^j个访问内，哪次访问的节点深度最小bool vis[100005];void add(int u, int v, int index){edge[cnt].v = v; edge[cnt].index = index; edge[cnt].next = head[u]; head[u] = cnt++;edge[cnt].v = u; edge[cnt].index = index; edge[cnt].next = head[v]; head[v] = cnt++;}void dfs(int u, int dep, int fa){index++;vis[u] = 1;first[u] = index;node[index] = u;depth[index] = dep;dis[u] = dep;father[u] = fa;for (int i = head[u]; i !=-1; i=edge[i].next){int v = edge[i].v;if (!vis[v]){dfs(v, dep + time[edge[i].index], u);index++;node[index] = u;depth[index] = dep;}}}void ST(int n){int k = log((double)n) / log(2.0);for (int i = 1; i <= n; i++)dp[i][0] = i;for (int j = 1; j <= k; j++)for (int i = 1; i + (1 << j) - 1 <= n; i++){int a = dp[i][j - 1];int b = dp[i + (1 << (j - 1))][j - 1];if (depth[a] < depth[b])dp[i][j] = a;elsedp[i][j] = b;}}int LCA(int u, int v){int i = first[u];int j = first[v];if (i > j)swap(i, j);int k = log(j - i + 1.0) / log(2.0);int a = dp[i][k];int b = dp[j - (1 << k) + 1][k];int x = (depth[a] < depth[b]) ? a : b;return node[x];}void solve(int u,int v){int lca = LCA(u, v);printf("%d\n", dis[u] + dis[v] - 2 * dis[lca]);}void update(int u,int t,int fa){for (int i = head[u]; i != -1; i = edge[i].next){int v = edge[i].v;if (father[v] == fa){dis[v] += t;update(v, t, v);}}}int main(){int u, v;int op;while (~scanf("%d%d%d", &n, &q, &s)){index = cnt = 0;memset(head, -1, sizeof(head));memset(vis, 0, sizeof(vis));depth[1] = 0;dis[1] = 0;memset(dp, 0, sizeof(dp));for (int i = 1; i < n; i++){scanf("%d%d%d", &u, &v, &time[i]);add(u, v, i);}dfs(1, 0, 1);ST(index);while (q--){scanf("%d", &op);if (op){int ith, w;scanf("%d%d", &ith, &w);int pos = (ith - 1) * 2;int x = edge[pos].v;int y = edge[pos + 1].v;int ww = time[ith];time[ith] = w;//数据要更新，记住if (dis[x] > dis[y])swap(x, y);int t = w - ww;dis[y] += t;update(y, t, y);}else{int x;scanf("%d", &x);solve(s, x);s = x;}}}return 0;}