zoj 1015 Fishing Net//弦圖的判定

整理一下亂七八糟的知識點

#include<cstring>
#include<cstdio>
using namespace std;
const int maxn = 1010;
const int inf = 100000000;
struct EDGE
{
    int v, next;
}edge[maxn * maxn];
bool use[maxn][maxn] , used[maxn];
int n , record[maxn] , cost[maxn] , m , rank[maxn];
int cnt, head[maxn];
void addedge(int u ,int v)
{
    edge[cnt].v = v;
    edge[cnt].next = head[u];
    head[u] = cnt++;
}
void init()
{
    cnt = 0;
    memset(head, -1, sizeof(head));
    memset(use , false , sizeof(use));
}
bool solve()
{
    memset(used , false , sizeof(used));
    memset(cost , 0 , sizeof(cost));
    int i , u , minimum , x , j;
    for(i = n; i >= 1; i--)
    {
        minimum = 0;
        u = 0;
        for(j = 0; j < n; j++)
        {
            if(!used[j] && cost[j] > minimum)
            {
                minimum = cost[j];
                u = j;
            }
        }
        used[u] = true;
        record[i] = u;
        rank[u] = i;
        for(int p = head[u]; p != -1; p = edge[p].next)
        if(!used[edge[p].v])  cost[edge[p].v]++;
    }
    for(i = 1; i <= n; i++)
    {
        x = record[i];
        minimum = inf;
        for(int p = head[x]; p != -1; p = edge[p].next)
        {
            if(rank[edge[p].v] > i && rank[edge[p].v] < minimum)
            {
                u = edge[p].v;
                minimum = rank[u];
            }
        }
        if(minimum != inf)
        {
            for(int p = head[x]; p != -1; p = edge[p].next)
            {
                if(rank[edge[p].v] > i && u != edge[p].v)
                {
                    if(!use[u][edge[p].v])
                        return false;
                }
            }
        }
    }
    return true;
}
int main()
{
    int i , a , b;
    while(scanf("%d%d" , &n , &m) != EOF)
    {
        if(n == 0 && m == 0) break;
        init();
        for(i = 0; i < m; i++)
        {
            scanf("%d%d" , &a , &b);
            addedge(a-1, b-1);
            addedge(b-1, a-1);
            use[a - 1][b - 1] = use[b - 1][a - 1] = true;
        }
        if(solve()) printf("Perfect\n\n");
        else printf("Imperfect\n\n");
    }
}