【每日一题】dfs序专题,求和
求和
https://ac.nowcoder.com/acm/problem/204871
Solution
#include <bits/stdc++.h> using namespace std; #define js ios::sync_with_stdio(false);cin.tie(0); cout.tie(0) #define all(__vv__) (__vv__).begin(), (__vv__).end() #define endl "\n" #define pai pair<int, int> #define ms(__x__,__val__) memset(__x__, __val__, sizeof(__x__)) typedef long long ll; typedef unsigned long long ull; typedef long double ld; inline ll read() { ll s = 0, w = 1; char ch = getchar(); for (; !isdigit(ch); ch = getchar()) if (ch == '-') w = -1; for (; isdigit(ch); ch = getchar()) s = (s << 1) + (s << 3) + (ch ^ 48); return s * w; } inline void print(ll x, int op = 10) { if (!x) { putchar('0'); if (op) putchar(op); return; } char F[40]; ll tmp = x > 0 ? x : -x; if (x < 0)putchar('-'); int cnt = 0; while (tmp > 0) { F[cnt++] = tmp % 10 + '0'; tmp /= 10; } while (cnt > 0)putchar(F[--cnt]); if (op) putchar(op); } inline ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; } ll qpow(ll a, ll b) { ll ans = 1; while (b) { if (b & 1) ans *= a; b >>= 1; a *= a; } return ans; } ll qpow(ll a, ll b, ll mod) { ll ans = 1; while (b) { if (b & 1)(ans *= a) %= mod; b >>= 1; (a *= a) %= mod; }return ans % mod; } const int dir[][2] = { {0,1},{1,0},{0,-1},{-1,0},{1,1},{1,-1},{-1,1},{-1,-1} }; const int MOD = 1e9 + 7; const int INF = 0x3f3f3f3f; const int N = 1e6 + 7; vector<int> edge[N]; int tot, val[N], l[N], r[N]; ll sum[N]; void dfs(int u, int tmp) { l[u] = ++tot; for (auto& v : edge[u]) { if (v == tmp) continue; dfs(v, u); } r[u] = tot; } int lowbit(int x) { return x & (-x); } void update(int x, int y) { for (; x < N; x += lowbit(x)) sum[x] += y; } ll query(int x) { ll res = 0; for (; x; x -= lowbit(x)) res += sum[x]; return res; } int main() { int T = 1; //T = read(); while (T--) { int n = read(), m = read(), s = read(); for (int i = 1; i <= n; ++i) val[i] = read(); for (int i = 1; i < n; ++i) { int u = read(), v = read(); edge[u].push_back(v); edge[v].push_back(u); } dfs(s, 0); for (int i = 1; i <= n; ++i) update(l[i], val[i]); while (m--) { int op = read(); if (op & 1) { int u = read(), x = read(); update(l[u], x); //单点修改 } else { int u = read(); print(query(r[u]) - query(l[u] - 1)); // 区间查询 } } } return 0; }
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