POJ 1986:Distance Queries(倍增求LCA)
http://poj.org/problem?id=1986
题意:给出一棵n个点m条边的树,还有q个询问,求树上两点的距离。
思路:这次学了一下倍增算法求LCA。模板。
dp[i][j]代表第i个点的第2^j个祖先是哪个点,dp[i][0] = i的第一个祖先 = fa[i]。转移方程:dp[i][j] = dp[dp[i][j-1][j-1]。
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
#define N 100010
struct Edge {
int v, nxt, w;
Edge () {}
Edge (int v, int nxt, int w) : v(v), nxt(nxt), w(w) {}
} edge[N];
int dp[N][], dep[N], dis[N], fa[N], head[N], tot, n; void Add(int u, int v, int w) {
edge[tot] = Edge(v, head[u], w); head[u] = tot++;
edge[tot] = Edge(u, head[v], w); head[v] = tot++;
} void DFS(int u) {
dp[u][] = fa[u];
for(int i = ; i <= ; i++) // 转移
dp[u][i] = dp[dp[u][i-]][i-];
for(int i = head[u]; ~i; i = edge[i].nxt) {
int v = edge[i].v;
if(v == fa[u]) continue;
fa[v] = u;
dep[v] = dep[u] + ;
dis[v] = dis[u] + edge[i].w;
DFS(v);
}
} int LCA(int x, int y) {
if(dep[x] < dep[y]) swap(x, y); //设x为较深的点
for(int i = ; i >= ; i--) // 让x跑到和y同一深度
if(dep[dp[x][i]] >= dep[y]) x = dp[x][i];
if(x == y) return x;
for(int i = ; i >= ; i--) // x和y同时向上跑
if(dp[x][i] != dp[y][i])
x = dp[x][i], y = dp[y][i];
return dp[x][];
} int main() {
int m, q;
while(~scanf("%d%d", &n, &m)) {
memset(dp, , sizeof(dp));
memset(dis, , sizeof(dis));
memset(dep, , sizeof(dep));
memset(head, -, sizeof(head));
tot = ; char s[];
for(int i = ; i < m; i++) {
int u, v, w;
scanf("%d%d%d%s", &u, &v, &w, s);
Add(u, v, w);
}
fa[] = ; dis[] = dep[] = ;
DFS();
scanf("%d", &q);
while(q--) {
int u, v;
scanf("%d%d", &u, &v);
printf("%d\n", dis[u] + dis[v] - dis[LCA(u, v)] * );
}
}
return ;
}
POJ 1986:Distance Queries(倍增求LCA)的更多相关文章
- poj 1986 Distance Queries 带权lca 模版题
Distance Queries Description Farmer John's cows refused to run in his marathon since he chose a pa ...
- POJ.1986 Distance Queries ( LCA 倍增 )
POJ.1986 Distance Queries ( LCA 倍增 ) 题意分析 给出一个N个点,M条边的信息(u,v,w),表示树上u-v有一条边,边权为w,接下来有k个询问,每个询问为(a,b) ...
- POJ 1986 Distance Queries LCA两点距离树
标题来源:POJ 1986 Distance Queries 意甲冠军:给你一棵树 q第二次查询 每次你问两个点之间的距离 思路:对于2点 u v dis(u,v) = dis(root,u) + d ...
- POJ 1986 Distance Queries / UESTC 256 Distance Queries / CJOJ 1129 【USACO】距离咨询(最近公共祖先)
POJ 1986 Distance Queries / UESTC 256 Distance Queries / CJOJ 1129 [USACO]距离咨询(最近公共祖先) Description F ...
- POJ 1986 Distance Queries 【输入YY && LCA(Tarjan离线)】
任意门:http://poj.org/problem?id=1986 Distance Queries Time Limit: 2000MS Memory Limit: 30000K Total ...
- POJ 1986 Distance Queries(Tarjan离线法求LCA)
Distance Queries Time Limit: 2000MS Memory Limit: 30000K Total Submissions: 12846 Accepted: 4552 ...
- poj 1986 Distance Queries LCA
题目链接:http://poj.org/problem?id=1986 Farmer John's cows refused to run in his marathon since he chose ...
- POJ 1986 - Distance Queries - [LCA模板题][Tarjan-LCA算法]
题目链接:http://poj.org/problem?id=1986 Description Farmer John's cows refused to run in his marathon si ...
- POJ 1986 Distance Queries (Tarjan算法求最近公共祖先)
题目链接 Description Farmer John's cows refused to run in his marathon since he chose a path much too lo ...
- poj 1986 Distance Queries(LCA)
Description Farmer John's cows refused to run in his marathon since he chose a path much too long fo ...
随机推荐
- “Rsync” could not be found on your PATH
Vagrant with VirtualBox on Windows10: “Rsync” could not be found on your PATH 使用agrant安装系统时,遇到的错误提示: ...
- ORM 集合
1.EF https://github.com/aspnet 2.Chloe.ORM http://www.cnblogs.com/so9527/p/5809089.html http://www ...
- delphi中获取memo鼠标所在位置的行和列(通过EM_GETRECT消息取得Rect后,自己算一下)
也是看别人写的,但是不容易找到,就转发一篇delphi版本的 function GetLine(X, Y: integer): TPoint;var OldFont : HFont; Hand : ...
- jquery 鼠标经过延时触发事件,jquery插件
jquery 鼠标经过延时触发事件. 用来做:鼠标经过选项卡,延时切换,鼠标经过商城分类延时显示,最好不过,防止用户随便滑动就切换了选项卡. 一.引入jq 二.加入以下插件代码 /* * 鼠标经过延时 ...
- wpf 事件参数 绑定到viewmdoel
public sealed class EventCommand : TriggerAction<DependencyObject> { public static readonly De ...
- 图像滤镜艺术---(Lightleaks Filter)漏光滤镜
原文:图像滤镜艺术---(Lightleaks Filter)漏光滤镜 (Lightleaks Filter)漏光滤镜 漏光拍摄其实就是一种摄影手法,最初是因为强烈光照导致相片交卷的过分曝光,最终在成 ...
- Win8 Metro(C#)数字图像处理--2.50图像运动模糊
原文:Win8 Metro(C#)数字图像处理--2.50图像运动模糊 [函数名称] 图像运动模糊算法 MotionblurProcess(WriteableBitmap src,int ...
- GIS基础软件及操作(八)
原文 GIS基础软件及操作(八) 练习八.地理建模 地理建模:Model Builder 土壤侵蚀危险性建模分析 认识ModelBuilder操作界面 1: 添加硬盘上的数据或工具到模型中,数据也可以 ...
- 遍历所有的XML
XmlElement rootElement = doc.DocumentElement; foreach (XmlElement childElement in rootElement) { //C ...
- Bigtable:结构化数据的分布式存储系统
Bigtable最初是谷歌设计用来存储大规模结构化数据的分布式系统,其可以在数以千计的商用服务器上存储高达PB级别的数据量.开源社区根据Bigtable的设计思路开发了HBase.其优势在于提供了高效 ...