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## Discussion of Problem 2030. Awesome Backup System

What is test case 21 about?
Posted by Schwinn 1 Sep 2016 20:02
#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9+7, BLOCK = 320;

int n, m, a[100001], p[100001], idx[100001], order[100001], lb[100001], rb[100001]; // lb and rb are indexed by bfs order, not vertex
bool mark[100001];
vector<int> g[100001];

struct coolsqrt { // sqrt decomposition
int f[100001], t[100001];
void init() { for(int i = 1; i <= n; i++) f[i] = a[order[i]]; }
void update(int l, int r, int v) {
for(int i = l; i % BLOCK; i++) {
f[i] = (f[i]+v)%MOD;
if(i == r) return;
}
int block = l/BLOCK + 1;
while(block < r/BLOCK) t[block++] += v, t[block] %= MOD;
for(int i = BLOCK*(r/BLOCK); i <= r; i++) f[i]  = (f[i]+v)%MOD;
}
int query(int i) { return (f[i] + t[i/BLOCK])%MOD; }
void putin() { for(int i = 1; i <= n; i++) cout << query(i) << ' '; cout << endl; }
} coolsqrt;

int main() {
cin >> n;
for(int i = 1; i <= n; i++) cin >> a[i];
for(int i = 1,u,v; i < n; i++) {
cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
queue<int> q;
q.push(1);
for(int i = 1, u = q.front(); i <= n; i++, q.pop(), u = q.front()) {
mark[u] = true;
idx[u] = i;
order[i] = u;
for(int v: g[u]) if(!mark[v]) q.push(v), p[v] = u;
}
assert(q.empty());
for(int i = 1; i <= n; i++) if(p[order[i]]) {
if(!lb[p[order[i]]]) lb[p[order[i]]] = i;
rb[p[order[i]]] = i;
}
coolsqrt.init();
cin >> m;
int inst,v;
while(m--) {
cin >> inst >> v;
if(inst == 1) {
coolsqrt.update(idx[p[v]], idx[p[v]], coolsqrt.query(idx[v]));
coolsqrt.update(lb[v], rb[v], coolsqrt.query(idx[v]));
// coolsqrt.putin();
} else {
cout << coolsqrt.query(idx[v]) << endl;
}
}
// for(int i = 1; i <= n; i++) cout << order[i] << ' ';
// cout << endl;
// for(int i = 1; i <= n; i++) cout << lb[i] << ' ' << rb[i] << endl;
}

Edited by author 01.09.2016 20:03

Edited by author 01.09.2016 20:03