zoj 2587(判定が一意かどうか)

#include<iostream>
#include<cstdio>
#include<cstring>
#include<set>
#include<cstdio>
#include<string>
using namespace std;
const int maxn=1650;
const int inf=30000000;
struct node
{
    int v,next;
    int val;
}s[10050*4];

int level[maxn];//     
int p[maxn];
int que[200050];//BFS        ，DFS       
int out[maxn];//DFS         
int ind;

inline void insert(int x,int y,int z)
{
    s[ind].v=y;
    s[ind].val=z;
    s[ind].next=p[x];
    p[x]=ind++;
    s[ind].v=x;
    s[ind].val=0;
    s[ind].next=p[y];
    p[y]=ind++;
}

void init()
{
    ind=0;
    memset(p,-1,sizeof(p));
}

int max_flow(int n,int source,int sink)
{
    int ret=0;
    int h=0,r=0;
    while(1)//DFS
    {
        int i;
        for(i=0;i<=n;++i)
         level[i]=0;
         h=0,r=0;
        level[source]=1;
        que[0]=source;
        while(h<=r)//BFS
        {
            int  t=que[h++];
            for(i=p[t];i!=-1;i=s[i].next)
            {
                if(s[i].val&&level[s[i].v]==0)
                {
                    level[s[i].v]=level[t]+1;
                    que[++r]=s[i].v;
                }
            }
        }
        if(level[sink]==0)break;//     
        for(i=0;i<=n;++i)
        out[i]=p[i];
        int  q=-1;
        while(1)
        {
            if(q<0)
            {
                int  cur=out[source];
                for(;cur!=-1;cur=s[cur].next)
                {
                    if(s[cur].val&&out[s[cur].v]!=-1&&level[s[cur].v]==2)
                    {
                        break;
                    }
                }
                if(cur>=0)
                {
                    que[++q]=cur;
                    out[source]=s[cur].next;
                }
                else
                {
                    break;
                }
            }
            int  u=s[que[q]].v;
            if(u==sink)//     
            {
                int  dd=inf;
                int  index=-1;
                for(i=0;i<=q;i++)
                {
                    if(dd>s[que[i]].val)
                    {
                        dd=s[que[i]].val;
                        index=i;
                    }
                }
                ret+=dd;
                for(i=0;i<=q;i++)
                {
                    s[que[i]].val-=dd;
                    s[que[i]^1].val+=dd;
                }
                for(i=0;i<=q;i++)
                {
                    if(s[que[i]].val==0)
                    {
                        q=index-1;
                        break;
                    }
                }
            }
            else
            {
                long cur=out[u];
                for(;cur!=-1;cur=s[cur].next)
                {
                    if(s[cur].val&&out[s[cur].v]!=-1&&level[u]+1==level[s[cur].v])
                    {
                        break;
                    }
                }
                if(cur!=-1)
                {
                    que[++q]=cur;
                    out[u]=s[cur].next;
                }
                else
                {
                    out[u]=-1;
                    q--;
                }
            }
        }
    }
    return ret;
}

int n,m;
int cnts, cntt;
int flag1[maxn], flag2[maxn];

void dfs1(int v)
{
    flag1[v] = 1;
    cnts++;
    for(int i = p[v]; i != 0; i = s[i].next){
        if(flag1[s[i].v]==0 && s[i].val)
            dfs1(s[i].v);
    }
}
void dfs2(int v)
{
    flag2[v] = 1;
    cntt++;
    for(int i = p[v]; i != 0; i = s[i].next){
        if(flag2[s[i].v]==0 && s[i^1].val)
            dfs2(s[i].v);
    }
}
int main()
{
   int u,v,c;
   int start;
   int end;
   while(scanf("%d%d%d%d",&n,&m,&start,&end)!=EOF)
   {
    if(n==0&&m==0&&start==0&&end==0)
       break;
    init();
    for(int i=1;i<=m;i++)
    {
        cin>>u>>v>>c;
        insert(u,v,c);
        insert(v,u,c);
    }
        int maxx=max_flow(n+3,start,end);;
        memset(flag1,0,sizeof(flag1));
        memset(flag2,0,sizeof(flag2));
        cnts = cntt = 0;
        dfs1(start);
        dfs2(end);
        if(cnts+cntt!=n)
             printf("AMBIGUOUS
");
        else printf("UNIQUE
");
  }
    return 0;
}