zoj 1060 Sorting It All Out(拓扑排序)

来源：互联网发布：sql语句修改字段编辑：程序博客网时间：2024/06/09 21:57
#include<bits/stdc++.h>using namespace std;vector< vector<char> >v;int n,m,use[30],cnt[30];char ans[30],s[10];int topsort(int x){    int i,j,t[30],f=1,r,c;    memset(ans,0,sizeof(ans));    for(i=0; i<30; i++) t[i]=cnt[i];    c=0;    r=0;    while(x--)    {        c=0;        for(i=0; i<n; i++)        {            if(t[i]==0)            {                j=i;                c++;            }        }        if(c>=1)        {            if(c>1) f=0;            for(i=0; i<v[j].size(); i++)            {                t[v[j][i]]--;            }            ans[r++]=j+'A';            t[j]=-1;            ans[r]=0;        }        else if(c==0)            return -1;    }    if(f)        return r;    else        return 0;}int main(){    int flag,i,num,ok,k;    while(~scanf("%d%d",&n,&m))    {        if(n==0&&m==0) break;        v.clear();        v.resize(n);        memset(use,0,sizeof(use));        memset(cnt,0,sizeof(cnt));        ok=0;        num=0;        for(i=0; i<m; i++)        {            scanf("%s",s);            cnt[s[2]-'A']++;            v[s[0]-'A'].push_back(s[2]-'A');            if(!use[s[0]-'A'])            {                num++;                use[s[0]-'A']=1;            }            if(!use[s[2]-'A'])            {                num++;                use[s[2]-'A']=1;            }            if(ok==0)            {                int t=topsort(num);                if(t==n)                {                    ok=1;                    k=i+1;                }                else if(t==-1)                {                    ok=-1;                    k=i+1;                }            }        }        if(!ok) printf("Sorted sequence cannot be determined.\n");        else if(ok==1) printf("Sorted sequence determined after %d relations: %s.\n",k,ans);        else printf("Inconsistency found after %d relations.\n",k);    }    return 0;}
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