Cod sursa(job #191740)

Utilizator cata00Catalin Francu cata00 Data 28 mai 2008 09:41:49
Problema Stramosi Scor 0
Compilator cpp Status done
Runda Arhiva de probleme Marime 1.42 kb
#include <stdio.h>
#include <stdlib.h>

typedef unsigned char byte;

typedef struct list {
  int v;
  struct list *next;
};

FILE *fin, *fout;
int n, numTests;
// a[n][k] = the node 2^k levels above n.
int a[250010][20];
list *children[250010];
int numUnknown;

void read() {
  int parent;
  fscanf(fin, "%d %d", &n, &numTests);
  for (int i = 1; i <= n; i++) {
    fscanf(fin, "%d", &parent);
    a[i][0] = parent;
    for (int j = 1; j < 20; j++) {
      a[i][j] = -1;
    }
    if (parent) {
      list *l = (list*)malloc(sizeof(list));
      l->v = i;
      l->next = children[parent];
      children[parent] = l;
    }
  }
  numUnknown = 0;
}

void df(int root) {
  int log = 1;
  int node = a[root][0];
  while (node) {
    node = a[node][log - 1];
    a[root][log++] = node;
  }

  for (list *l = children[root]; l; l = l->next) {
    df(l->v);
  }
}

void preprocess() {
  for (int i = 1; i <= n; i++) {
    if (!a[i][0]) {
      df(i);
    }
  }
}

int query(int node, int level) {
  int log = 0;
  while (level && node) {
    if (level % 2) {
      node = a[node][log];
    }
    log++;
    level >>= 1;
  }
  return node;
}

int main() {
  fin = fopen("stramosi.in", "rt");
  fout = fopen("stramosi.out", "wt");
  read();
  preprocess();

  for (int test = 0; test < numTests; test++) {
    int node, level;
    fscanf(fin, "%d %d", &node, &level);
    fprintf(fout, "%d\n", query(node, level));
  }

  fclose(fin);
  fclose(fout);
  return 0;
}