Submission #1042390

#	Time	Username	Problem	Language	Result	Execution time	Memory
1042390		sleepntsheep	Inside information (BOI21_servers)	C11	50 / 100	3544 ms	27828 KiB

servers

#include <stdio.h>
#include <stdlib.h>

/*
 * For "Q" queries, use LCA + prefix sum on tree ~ 3O(lgn) [for finding lca and almost-lca]
 *
 *
 * Every B queries of any type, do naive dp on tree (reverse edge order)
 * to find answer for "C" queries  ~ O(n)
 *
 * On "C" queries, use cached answer from above and count all edges that appeared after that (by "Q")
 * ~ O(B lgn)
 *
 *
 * Time complexity = O(N^2 / B) + O(N lgn) + O(N B lgn)
 *
 * Let B = sqrt(N / lgN)
 */

#define N 1200010
#define B 300


int n, q, pp[N], jj[N], dd[N], up[N], temp, inc[N], map_time[N];

void pus_(int **eh, int *eo, int i, int j) {
    int o = eo[i]++;
    if (0 == o) eh[i] = (int*)malloc(2 * sizeof **eh);
    else if (0 == (o & o - 1)) eh[i] = (int*)realloc(eh[i], 2 * o * sizeof **eh);
    eh[i][o] = j;
}

int *eh[N], *fh[N], eo[N];

void link(int u, int v, int w) {
    pus_(eh, eo, u, v);
    --eo[u];
    pus_(fh, eo, u, w);
    pus_(eh, eo, v, u);
    --eo[v];
    pus_(fh, eo, v, w);
}

void dfs(int u, int p) {
    inc[u] = (up[u] > up[p]) + inc[p];
    for (int j = 0; j < eo[u]; ++j) if (eh[u][j] != p) {
        int v = eh[u][j];
        dd[v] = dd[u] + 1;
        pp[v] = u;
        jj[v] = (dd[u] - dd[jj[u]] == dd[jj[u]] - dd[jj[jj[u]]]) ? jj[jj[u]]: u;

        up[v] = fh[u][j];
        dfs(v, u);
    }
}

int lca(int u, int v) {
    while (dd[u] != dd[v]) {
        if (dd[u] < dd[v]) temp = u, u = v, v = temp;
        u = (dd[jj[u]] >= dd[v]) ? jj[u] : pp[u];
    }
    while (u != v)
        if (jj[u] != jj[v]) u = jj[u], v = jj[v];
        else u = pp[u], v = pp[v];
    return u;
}

int anc(int u, int dep) {
    while (dd[u] > dep)
        u = (dd[jj[u]] >= dep) ? jj[u] : pp[u];
    return u;
}

struct Query {
    char type;
    int a, b;
    int ans;
} qq[N * 2];

/* u = data node, v = ask node */
int query_yesno(int u, int v, int time) {
    if (u == v) return 1;
    int a = lca(u, v);
    int va = anc(v, dd[a] + 1);
    int ua = anc(u, dd[a] + 1);

    if (u == a)
        return inc[v] - inc[va] == dd[v] - dd[va] && up[v] <= time;
    if (v == a)
        return inc[u] - inc[ua] == 0 && up[ua] <= time;

    return (dd[v] - dd[va] == inc[v] - inc[va]) && (inc[u] - inc[ua] == 0)
        && up[va] > up[ua] && up[v] <= time;
}

int dp[N], comp[N];

void efs(int u, int p, int time, int root) {
    comp[u] = root;
    for (int j = 0; j < eo[u]; ++j)
        if (eh[u][j] != p && fh[u][j] <= time && comp[eh[u][j]] == -1)
            efs(eh[u][j], u, time, root);
}

void build(int ii, int tme) {
    for (int i = 1; i <= n; ++i)
        dp[i] = 1, comp[i] = -1;

    for (int i = ii; i >= 0; --i) {
        if (qq[i].type != 'S')
            continue;

        int x = dp[qq[i].a], y = dp[qq[i].b];
        dp[qq[i].a] += y;
        dp[qq[i].b] += x;
    }

    for (int i = 1; i <= n; ++i)
        if (comp[i] == -1)
            efs(i, i, tme, i);
}

int counted[N];

int main() {
    scanf("%d%d", &n, &q);

    q = n + q - 1;
    for (int j = 0, i = 0; i < q; ++i) {
        char c;
        int a, b;
        scanf(" %c%d", &c, &a);
        if (c == 'S') {
            scanf("%d", &b);
            link(a, b, j++);
            map_time[j - 1] = i;
        } else if (c == 'Q')
            scanf("%d", &b);

        qq[i] = (struct Query){c, a, b};
    }

    up[1] = 1e9;
    pp[1] = jj[1] = 1;
    dfs(1, 1);

    build(-1, -1);
    int at = 0;

    for (int j = 0, i = 0; i < q; ++i) {
        if (qq[i].type == 'S') {
            ++j;
        }
        else if (qq[i].type == 'Q') {
            puts(query_yesno(qq[i].b, qq[i].a, j - 1) ? "yes": "no");
        } else {
            int focus = qq[i].a;
            int addition = 0;
            for (int k = at; k < i; ++k)
                if (qq[k].type == 'S') {
                    int a = qq[k].a, b = qq[k].b;

                    if (counted[a] != i + 1 &&
                            comp[a] != comp[focus] && query_yesno(focus, a, j - 1))
                        ++addition, counted[a] = i + 1;
                    if (counted[b] != i + 1 && 
                            comp[b] != comp[focus] && query_yesno(focus, b, j - 1))
                        ++addition, counted[b] = i + 1;
                }
            printf("%d\n", dp[focus] + addition);
        }

        if (i % B == 0) {
            build(i, j);
            at = i + 1;
        }
    }
}

Compilation message (stderr)

servers.c: In function 'pus_':
servers.c:30:26: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   30 |     else if (0 == (o & o - 1)) eh[i] = (int*)realloc(eh[i], 2 * o * sizeof **eh);
      |                        ~~^~~
servers.c: In function 'main':
servers.c:127:5: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
  127 |     scanf("%d%d", &n, &q);
      |     ^~~~~~~~~~~~~~~~~~~~~
servers.c:133:9: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
  133 |         scanf(" %c%d", &c, &a);
      |         ^~~~~~~~~~~~~~~~~~~~~~
servers.c:135:13: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
  135 |             scanf("%d", &b);
      |             ^~~~~~~~~~~~~~~
servers.c:139:13: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
  139 |             scanf("%d", &b);
      |             ^~~~~~~~~~~~~~~

• Subtask 1: 2.5 / 2.5
• Subtask 2: 0 / 2.5
• Subtask 3: 2.5 / 2.5
• Subtask 4: 0 / 2.5
• Subtask 5: 5 / 5
• Subtask 6: 0 / 5
• Subtask 7: 10 / 10
• Subtask 8: 0 / 10
• Subtask 9: 12.5 / 12.5
• Subtask 10: 0 / 12.5
• Subtask 11: 17.5 / 17.5
• Subtask 12: 0 / 17.5