poj3099

bfs

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

#define maxn 2005
#define inf 0x3f3f3f3f

struct Edge
{
    int v, next;
}edge[maxn];

struct Point
{
    int x, y, z;
}point[maxn];

struct Node
{
    int d, v;
}q[maxn];

int n, id[maxn];
int head[maxn];
int length[maxn];
int ecount;
bool vis[maxn];

int dist(Point &a, Point &b)
{
    Point c;
    c.x = a.x - b.x;
    c.y = a.y - b.y;
    c.z = a.z - b.z;
    return c.x * c.x + c.y * c.y + c.z * c.z;
}

void addedge(int a, int b)
{
    edge[ecount].next = head[a];
    edge[ecount].v = b;
    head[a] = ecount++;
}

void input()
{
    scanf("%d%d%d%d", &id[0], &point[0].x, &point[0].y, &point[0].z);
    memset(head, -1, sizeof(head));
    ecount = 0;
    for (int i = 1; i < n; i++)
    {
        int mind = inf;
        int mini;
        scanf("%d%d%d%d", &id[i], &point[i].x, &point[i].y, &point[i].z);
        for (int j = 0; j < i; j++)
        {
            int temp = dist(point[i], point[j]);
            if (temp < mind)
            {
                mini = j;
                mind = temp;
            }
        }
        addedge(i, mini);
        addedge(mini, i);
    }
}

int bfs(int a)
{
    int front = 0;
    int rear = 1;
    int ret = 0;
    memset(vis, 0, sizeof(vis));
    q[0].d = 0;
    q[0].v = a;
    vis[a] = true;
    while (front != rear)
    {
        Node temp = q[front++];
        if (front == maxn)
            front = 0;
        if (temp.d > ret)
            ret = temp.d;
        for (int i = head[temp.v]; i != -1; i = edge[i].next)
        {
            int v = edge[i].v;
            if (!vis[v])
            {
                q[rear].v = v;
                q[rear].d = temp.d + 1;
                rear++;
                if (rear == maxn)
                    rear = 0;
                vis[v] = true;
            }
        }
    }
    return ret;
}

int main()
{
    //freopen("t.txt", "r", stdin);
    while (scanf("%d", &n), n)
    {
        input();
        memset(length, 0, sizeof(length));
        for (int i = 0; i < n; i++)
            length[i] = bfs(i);
        int len = inf;
        int ans1 = -1, ans2 = -1;
        for (int i = 0; i < n; i++)
            if (length[i] < len)
            {
                len = length[i];
                ans1 = i;
                ans2 = -1;
            }else if (length[i] == len)
                ans2 = i;
        if (-1 == ans2)
            printf("%d\n", id[ans1]);
        else
        {
            if (id[ans1] > id[ans2])
                swap(ans1, ans2);
            printf("%d %d\n", id[ans1], id[ans2]);
        }
    }
    return 0;
}