[HDU 5039 Hilarity] DFS序+线段树

题目

http://acm.hdu.edu.cn/showproblem.php?pid=5039

分析

DFS序+线段树

由于异或运算的特殊性，两点间的异或值等于两点到根的异或值的异或

所以答案为到根的异或值为1的点数*到根的异或值为0的点数*2

线段树维护DFS序维护区间和即可

代码

/**************************************************
 *        Problem:  HDU 5039
 *         Author:  clavichord93
 *          State:  Accepted
 **************************************************/

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <map>
using namespace std;

const int MAX_E = 60005;
const int MAX_N = 30005;

struct Edge {
    int dest;
    int id;
    int cost;
    Edge *next;
    Edge() {}
    Edge(int _dest, int _id, int _cost, Edge *_next) : dest(_dest), id(_id), cost(_cost), next(_next) {}
};

Edge EdgePool[MAX_E];
Edge *EP;
Edge *e[MAX_N];

int n;
map<string, int> name;
char s[100];
char t[100];

int ind;
int st[MAX_N];
int en[MAX_N];
int seq[MAX_N];
int value[MAX_N];
int next[MAX_N];

int sum[MAX_N << 2];
bool tag[MAX_N << 2];

inline void addedge(int a, int b, int c, int id) {
    e[a] = new(EP++)Edge(b, id, c, e[a]);
    e[b] = new(EP++)Edge(a, id, c, e[b]);
}

void dfs(int i, int parent) {
    st[i] = ++ind;
    seq[ind] = i;
    for (Edge *j = e[i]; j; j = j->next) {
        if (j->dest != parent) {
            next[j->id] = j->dest;
            value[j->dest] = value[i] ^ j->cost;
            dfs(j->dest, i);
        }
    }
    en[i] = ind;
}

#define lch(t) (t << 1)
#define rch(t) (t << 1 | 1)

void makeTree(int t, int l, int r) {
    if (l == r) {
        sum[t] = value[seq[l]];
        tag[t] = 0;
    }
    else {
        int mid = (l + r) >> 1;
        makeTree(lch(t), l, mid);
        makeTree(rch(t), mid + 1, r);
        sum[t] = sum[lch(t)] + sum[rch(t)];
        tag[t] = 0;
    }
}

void pushdown(int t, int l, int r) {
    if (tag[t]) {
        int lt = lch(t);
        int rt = rch(t);
        int mid = (l + r) >> 1;

        sum[lt] = mid - l + 1 - sum[lt];
        tag[lt] ^= 1;
        sum[rt] = r - mid - sum[rt];
        tag[rt] ^= 1;

        tag[t] = 0;
    }
}

void reverse(int t, int l, int r, int x, int y) {
    if (x <= l && r <= y) {
        sum[t] = r - l + 1 - sum[t];
        tag[t] ^= 1;
    }
    else {
        pushdown(t, l, r);
        int mid = (l + r) >> 1;
        if (x <= mid) {
            reverse(lch(t), l, mid, x, y);
        }
        if (y > mid) {
            reverse(rch(t), mid + 1, r, x, y);
        }
        sum[t] = sum[lch(t)] + sum[rch(t)];
    }
}

#undef lch
#undef rch

int main() {
    #ifdef LOCAL_JUDGE
    freopen("in.txt", "r", stdin);
    #endif
    int T;
    scanf("%d", &T);
    for (int cas = 1; cas <= T; cas++) {
        EP = EdgePool;
        memset(e, 0, sizeof(e));
        name.clear();

        scanf("%d", &n);
        for (int i = 1; i <= n; i++) {
            scanf("%s", s);
            string t(s);
            name[t] = i;
        }
        for (int i = 1; i < n; i++) {
            int val;
            scanf("%s %s %d", s, t, &val);
            string a(s);
            string b(t);
            int u = name[a];
            int v = name[b];
            addedge(u, v, val, i);
        }

        ind = 0;
        memset(st, 0, sizeof(st));
        memset(en, 0, sizeof(en));
        memset(seq, 0, sizeof(seq));
        memset(value, 0, sizeof(value));
        memset(next, 0, sizeof(next));
        dfs(1, 0);

        makeTree(1, 1, n);
        int m;
        scanf("%d", &m);
        printf("Case #%d:\n", cas);
        for (int i = 0; i < m; i++) {
            scanf("%s", s);
            if (s[0] == 'M') {
                int x;
                scanf("%d", &x);
                x = next[x];
                reverse(1, 1, n, st[x], en[x]);
            }
            else {
                printf("%I64d\n", (long long)sum[1] * (n - sum[1]) * 2);
            }
        }
    }

    return 0;
}