Codeforces 383C Propagating tree DFS序+BIT 一颗以1为根节点的树,两种操作,1 x c 将节点x值+c,节点x的所有孩子的值-c,所有孩子的孩子的节点+c...交替正负直到叶子节点;2 x 查询节点x当前的值。挺简单的一题..当时怎么就没去看...这题只要能想到时间戳的话,就简单了..首先dfs遍历树打上时间戳,这样...
tree[pos<<1].v+=tree[pos].mark; tree[pos<<1].mark+=tree[pos].mark; tree[pos<<1|1].v+=tree[pos].mark; tree[pos<<1|1].mark+=tree[pos].mark; tree[pos].mark=0; } } voidupdate(intL,intR,intv,intpos){ if(L<=tree[pos].l&&R>=tree[pos].r){ tree[pos].v+=v; tree...
"inline")#pragmaGCC optimize(2)#include<bits/stdc++.h>usingnamespacestd;typedeflonglongll;typedefunsignedlonglongull;typedefpair<ll,ll>PLL;typedefpair<int,int>PII;typedefpair<double,double>PDD;#defineI_int llinlinellread(){
The back-edges of the graph all connect a vertex with its descendant in the spanning tree. The explanation helped a lot. Thanks. → Reply iynaur87 5 years ago, # | 0 https://codeforces.com/contest/1364/problem/D A new problem that can be solved by getting a cycle that doesn't...
Codeforces 570D TREE REQUESTS dfs序+树状数组 题意: 给定n个点的树,m个询问 下面n-1个数给出每个点的父节点,1是root 每个点有一个字母 下面n个小写字母给出每个点的字母。 下面m行给出询问: 询问形如 (u, deep) 问u点的子树中,距离根的深度为deep的所有点的字母能否在任意排列后组成回文串,能输出...
根据lowbit(x)的值,新定义一个数组tree[i]= a_{i-lowbit(i)+1}+...+a_i 。那么区间求和就可以通过lowbit操作拆分成多个tree的累加,例如: sum[8]=tree[8] sum[7]=tree[7]+tree[6]+tree[4] ... 而在更新的时候,这个过程刚好是逆向的。例如改变 a_3 ,那么tree[3]、tree[4]、tree[8]等都会...
E. Tree Queries 原题指路: codeforces.com/problems 题意(2 s) 给定一棵包含编号1∼n的n (2≤n≤2e5)个节点的树, 其中节点1为根节点. 给定m (1≤m≤2e5)个询问, 每个询问给定一个包含k (1≤k≤n)个节点的集合v=[v1,⋯,vk] (1≤vi≤n), 表示询问是否存在一条从根节点1到某个节点u的...
DFS (Depth First Search) is an algorithm used to traverse graph or tree. We first select the root node of a tree, or any random node(in case of graph) and explore as far as possible in a branch and then come back to a fixed point. DFS is generally used for connectivity questions....
codeforces 982C的dfs算法复杂度是多少? codeforces 982C的dfs如何优化? 题意描述 You’re given a tree with n vertices. Your task is to determine the maximum possible number of edges that can be removed in such a way that all the remaining connected components will have even size. 给定一棵树...
CodeForces - 717E 的时间复杂度是多少? BUPT 2017 summer training (for 16) #1H 题意 每个节点是黑色or白色,经过一个节点就会改变它的颜色,一开始在1节点。求一条路径使得所有点变成黑色。 题解 dfs时每个节点的孩子处理完,这时候如果颜色是白色,那么再去一下父亲节点再回来,就变成黑色了。 如果是1号点,...