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Cod sursa(job #601267)
#include<stdio.h>
#include<malloc.h>
#define MaxN 250100
#define MaxlgN 51
typedef struct _nod
{
int info;
struct _nod *adr;
} nod;
typedef struct
{
struct _nod *cap;
} list;
list A[MaxN];
int V[MaxN];
int viz[MaxN];
int B[MaxN][MaxlgN];
int N;
int M;
int a;
int b;
void add(int a,int b)
{
nod *nou = (nod*)malloc(sizeof(nod));
nou->info = b;
nou->adr = A[a].cap;
A[a].cap = nou;
}
void citire(FILE *f)
{
int a;
fscanf(f,"%d %d",&N,&M);
for(int i=1;i<=N;i++)
{
fscanf(f,"%d ",&a);
if(a)
{
add(i,a);
add(a,i);
}
}
}
void Complet(int a,int k)
{
B[a][0] = k-1;
for(int i=1;i<k;i*=2)
B[a][i] = V[k-i];
}
void DF(int a,int k)
{
viz[a] = 1;
V[k] = a;
Complet(a,k);
nod *q = A[a].cap;
while(q)
{
if(!viz[q->info])
DF(q->info,k+1);
q = q->adr;
}
}
int LogDoiDinK(int &k)
{
int nr = 0;
int log = 1;
while(k>log)
{
log *= 2;
++nr;
}
k -= log != 1 ? (log/2) : 1;
return log == 1 ? 1:nr;
}
int FindStra(int a,int k)
{
if(k == 0)
return a;
int nr = LogDoiDinK(k);
if(B[a][0] < nr)
return 0;
return FindStra(B[a][nr],k);
}
void CompletGraph(void)
{
for(int i=1;i<=N;i++)
if(!viz[i])
DF(i,1);
}
int main()
{
FILE *f = fopen("stramosi.in","r");
FILE *g = fopen("stramosi.out","w");
citire(f);
CompletGraph();
for(int i=1;i<=M;i++)
{
fscanf(f,"%d %d",&a,&b);
fprintf(g,"%d\n",FindStra(a,b));
}
fclose(g);
fclose(f);
return 0;
}