Codeforces 877E Danil and a Part-time Job（dfs序+线段树）

Danil decided to earn some money, so he had found a part-time job. The interview have went well, so now he is a light switcher.

Danil works in a rooted tree (undirected connected acyclic graph) with n vertices, vertex 1 is the root of the tree. There is a room in each vertex, light can be switched on or off in each room. Danil’s duties include switching light in all rooms of the subtree of the vertex. It means that if light is switched on in some room of the subtree, he should switch it off. Otherwise, he should switch it on.

Unfortunately (or fortunately), Danil is very lazy. He knows that his boss is not going to personally check the work. Instead, he will send Danil tasks using Workforces personal messages.

There are two types of tasks:

pow v describes a task to switch lights in the subtree of vertex v.
get v describes a task to count the number of rooms in the subtree of v, in which the light is turned on. Danil should send the answer to his boss using Workforces messages.
A subtree of vertex v is a set of vertices for which the shortest path from them to the root passes through v. In particular, the vertex v is in the subtree of v.

Danil is not going to perform his duties. He asks you to write a program, which answers the boss instead of him.

Input
The first line contains a single integer n (1 ≤ n ≤ 200 000) — the number of vertices in the tree.

The second line contains n - 1 space-separated integers p2, p3, …, pn (1 ≤ pi < i), where pi is the ancestor of vertex i.

The third line contains n space-separated integers t1, t2, …, tn (0 ≤ ti ≤ 1), where ti is 1, if the light is turned on in vertex i and 0 otherwise.

The fourth line contains a single integer q (1 ≤ q ≤ 200 000) — the number of tasks.

The next q lines are get v or pow v (1 ≤ v ≤ n) — the tasks described above.

Output
For each task get v print the number of rooms in the subtree of v, in which the light is turned on.

Example
Input
4
1 1 1
1 0 0 1
9
get 1
get 2
get 3
get 4
pow 1
get 1
get 2
get 3
get 4
Output
2
0
0
1
2
1
1
0

神奇的区间更新操作，（mid - l + 1），区间01反转后的和即为区间长度减本身

public class Main {
    static int[] start = new int[200005];
    static int[] end = new int[200005];
    static int[] light = new int[200005];
    static int[] dfsOrder = new int[200005];
    static int[] sum = new int[200005 << 2 | 1];
    static int[] lazy = new int[200005 << 2 | 1];
    static int index = 0;
    @SuppressWarnings("unchecked")
    static ArrayList G[] = new ArrayList[200005];

    public static void main(String[] args) {
        Scanner reader = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
        int n = reader.nextInt();

        for (int i = 1; i <= n; i++) {
            G[i] = new ArrayList<>();
        }

        for (int i = 2; i <= n; i++) {
            int p = reader.nextInt();
            G[p].add(i);
        }

        for (int i = 1; i <= n; i++) {
            light[i] = reader.nextInt();
        }
        dfs(1);
        build(1, 1, n);
        int q = reader.nextInt();
        while (q-- > 0) {
            String com = reader.next();
            int c = reader.nextInt();
            if (com.charAt(0) == 'g') {
                int ans = query(1, start[c], end[c], 1, n);
                out.println(ans);
            } else {
                update(1, start[c], end[c], 1, n);
            }
        }
        out.close();
    }

    public static void build(int i, int l, int r) {
        if (r == l) {
            sum[i] = light[dfsOrder[l]];
            return;
        }
        int mid = (l + r) / 2;
        build(i << 1, l, mid);
        build(i << 1 | 1, mid + 1, r);
        pushUp(i);
    }

    public static void pushUp(int i) {
        sum[i] = sum[i << 1] + sum[i << 1 | 1];
    }

    public static void update(int i, int L, int R, int l, int r) {
        if (l >= L && r <= R) {
            sum[i] = (r - l + 1) - sum[i];
            lazy[i] ^= 1;
            return;
        }
        pushDown(i, l, r);
        int mid = (l + r) / 2;
        if (L <= mid) {
            update(i << 1, L, R, l, mid);
        }
        if (R > mid) {
            update(i << 1 | 1, L, R, mid + 1, r);
        }
        pushUp(i);
    }

    public static int query(int i, int L, int R, int l, int r) {
        if (l >= L && r <= R) {
            return sum[i];
        }
        pushDown(i, l, r);
        int ans = 0;
        int mid = (l + r) / 2;
        if (L <= mid) {
            ans += query(i << 1, L, R, l, mid);
        }
        if (R > mid) {
            ans += query(i << 1 | 1, L, R, mid + 1, r);
        }
        pushUp(i);
        return ans;
    }

    public static void pushDown(int i, int l, int r) {
        if (lazy[i] == 0) {
            return;
        }
        int mid = (l + r) / 2;
        sum[i << 1] = (mid - l + 1) - sum[i << 1];
        lazy[i << 1] ^= 1;
        sum[i << 1 | 1] = (r - mid - 1 + 1) - sum[i << 1 | 1];
        lazy[i << 1 | 1] ^= 1;
        lazy[i] = 0;
    }

    public static void dfs(int x) {
        start[x] = ++index;
        // System.out.print(x);
        dfsOrder[index] = x;
        for (int i = 0; i < G[x].size(); i++) {
            int get = G[x].get(i);
            dfs(get);
        }
        // System.out.print(x);
        end[x] = index;
    }

}