#144. DFS 序 1

https://loj.ac/s/2120655

LibreOJ/144/144.cpp

@@ -0,0 +1,88 @@
+#include <iostream>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e6 + 5;
+
+int n, m, r, v[N];
+long long f[N];
+int cnt, in[N], out[N];
+std::vector<int> g[N];
+
+int lowbit(int x) {
+    return x & -x;
+}
+
+void add(int x, int y) {
+    for (int i = x; i <= n; i += lowbit(i)) {
+        f[i] += y;
+    }
+}
+
+long long query(int x) {
+    long long res = 0;
+
+    for (int i = x; i; i -= lowbit(i)) {
+        res += f[i];
+    }
+
+    return res;
+}
+
+void dfs(int u, int f) {
+    in[u] = ++cnt;
+    add(cnt, v[u]);
+
+    for (int v : g[u]) {
+        if (v == f) continue;
+
+        dfs(v, u);
+    }
+
+    out[u] = cnt;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m >> r;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> v[i];
+    }
+
+    for (int i = 1, u, v; i < n; i++) {
+        cin >> u >> v;
+
+        g[u].emplace_back(v);
+        g[v].emplace_back(u);
+    }
+
+    dfs(r, 0);
+
+    while (m--) {
+        int op;
+
+        cin >> op;
+
+        if (op == 1) {
+            int a, x;
+
+            cin >> a >> x;
+
+            add(in[a], x);
+        } else {  // op == 2
+            int a;
+
+            cin >> a;
+
+            cout << query(out[a]) - query(in[a] - 1) << endl;
+        }
+    }
+
+    return 0;
+}