HELP!My algo:find the minimum,add the edge,sort and print,the first and the third step I use the heap.I don't think these matter.
My code:

#include<iostream>
using namespace std;
const int maxn = 7500;
int heap_size = 0, now = 0;
int heap[maxn + 1];
struct edge
{
    int neighbour;
    edge *pre;
}e[maxn + 1];
edge *tail[maxn + 1];
inline void swap(int i, int j)
{
    int temp;
    temp = heap[i];
    heap[i] = heap[j];
    heap[j] = temp;
    return;
}
void heap_up(int i)
{
    if (i == 1) return;
    int father = i / 2;
    if (heap[i] < heap[father])
    {
        swap(i, father);
        heap_up(father);
    }
    return;
}
void heap_down(int i)
{
    int left = i * 2;
    int right = left + 1;
    int least = i;
    if (left <= heap_size && heap[left] < heap[least]) least = left;
    if (right <= heap_size && heap[right] < heap[least]) least = right;
    if (least != i)
    {
        swap(i, least);
        heap_down(least);
    }
    return;
}
inline void heap_delete(int i)
{
    swap(i, heap_size--);
    heap_down(i);
    return;
}
inline void heap_insert(int key)
{
    heap[++heap_size] = key;
    heap_up(heap_size);
    return;
}
inline void connect(int u, int v)
{
    e[++now].neighbour = v;
    e[now].pre = tail[u];
    tail[u] = e + now;
    return;
}
int main()
{
    int son[maxn + 1] = { 0 }, code[maxn];
    int n = 1, i, u, v, temp;
    do
    {
        temp = 0;
        cin >> temp;
        if (temp)
        {
            code[n++] = temp;
            son[temp]++;
        }
    } while (temp);
    for (i = 1; i <= n; i++) if (!son[i]) heap_insert(i);
    for (i = 1; i <= n; i++) tail[i] = nullptr;
    for (i = 1; i < n; i++)
    {
        v = heap[1];
        heap_delete(1);
        u = code[i];
        if (!(--son[u])) heap_insert(u);
        connect(u, v);
        connect(v, u);
    }
    edge *p;
    heap_size = 0;
    for (i = 1; i <= n; i++)
    {
        cout << i << ":";
        for (p = tail[i]; p != nullptr; p = p->pre) heap_insert(p->neighbour);
        for (; heap_size; heap_delete(1)) cout << " " << heap[1];
        cout << endl;
    }
    return 0;
}

Edited by author 06.02.2015 21:40

Edited by author 07.02.2015 08:44

Somewhere there should be bad indexing. Try to increase arrays size from maxn + 1 to maxn + 50 and check what results judge gives.