CodeForces 384E Propagating tree (线段树+dfs)

时间:2023-03-09 18:52:41
CodeForces 384E Propagating tree (线段树+dfs)

题意:题意很简单么,给定n个点,m个询问的无向树(1为根),每个点的权值,有两种操作,

第一种:1 x v,表示把 x 结点加上v,然后把 x 的的子结点加上 -v,再把 x 的子结点的子结点加上 -(-v),依次。。。

第二种:2 x, 表示查询 x 结点的权值。

析:因为这是一棵树,很难维护,所以可以考虑先用 dfs 记录每个结点的开始和结束的时间戳,而位于开始和结束时间戳内的就是就是它的子孙结点,

这样就能维护两棵线段树,一棵是奇数层的, 一棵是偶数层的,每次执行 1 操作就把相应的结点的开始和结束作为一个区间进行更新,然后再执行

相反层的 -v 进行更新。当查询的时候,就直接输出相应层的输出再加原来权值即可。

代码如下:

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include <cstdio>
#include <string>
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <cstring>
#include <set>
#include <queue>
#include <algorithm>
#include <vector>
#include <map>
#include <cctype>
#include <cmath>
#include <stack>
#include <sstream>
#define debug() puts("++++");
#define gcd(a, b) __gcd(a, b)
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define freopenr freopen("in.txt", "r", stdin)
#define freopenw freopen("out.txt", "w", stdout)
using namespace std; typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int, int> P;
const int INF = 0x3f3f3f3f;
const LL LNF = 1e16;
const double inf = 0x3f3f3f3f3f3f;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int maxn = 200000 + 10;
const int mod = 1000000007;
const int dr[] = {-1, 0, 1, 0};
const int dc[] = {0, 1, 0, -1};
const char *de[] = {"0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111", "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111"};
int n, m;
const int mon[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
const int monn[] = {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
inline bool is_in(int r, int c){
return r >= 0 && r < n && c >= 0 && c < m;
} int dfsnum[maxn], in[maxn];
int a[maxn], out[maxn], dep[maxn];
int sum[2][maxn<<2], addv[2][maxn<<2];
vector<int> G[maxn];
int cnt; void dfs(int u, int fa, int d){
dep[u] = d;
in[u] = ++cnt; for(int i = 0; i < G[u].size(); ++i){
int v = G[u][i];
if(v == fa) continue;
dfs(v, u, d+1);
}
out[u] = cnt;
} void push_down(int *sum, int rt, int *addv){
if(addv[rt] == 0) return ;
int l = rt<<1, r = rt<<1|1;
sum[l] += addv[rt];
sum[r] += addv[rt];
addv[l] += addv[rt];
addv[r] += addv[rt];
addv[rt] = 0;
} void update(int *sum, int *addv, int L, int R, int val, int l, int r, int rt){
if(L <= l && r <= R){
addv[rt] += val;
sum[rt] += val;
return ;
}
push_down(sum, rt, addv);
int m = l + r >> 1;
if(L <= m) update(sum, addv, L, R, val, lson);
if(R > m) update(sum, addv, L, R, val, rson);
} int query(int *sum, int *addv, int M, int l, int r, int rt){
if(l == r) return sum[rt];
push_down(sum, rt, addv);
int m = l + r >> 1;
if(M <= m) return query(sum, addv, M, lson);
return query(sum, addv, M, rson);
} int main(){
scanf("%d %d", &n, &m);
for(int i = 1; i <= n; ++i) scanf("%d", a+i);
for(int i = 1; i < n; ++i){
int u, v;
scanf("%d %d", &u, &v);
G[u].push_back(v);
G[v].push_back(u);
}
dfs(1, -1, 1);
while(m--){
int x, c, op;
scanf("%d %d", &op, &x);
int t = dep[x]&1;
if(op == 1){
scanf("%d", &c);
update(sum[t], addv[t], in[x], out[x], c, 1, n, 1);
if(in[x] < out[x])
update(sum[t^1], addv[t^1], in[x]+1, out[x], -c, 1, n, 1);
}
else printf("%d\n", query(sum[t], addv[t], in[x], 1, n, 1) + a[x]);
}
return 0;
}