拓扑排序,好麻烦的说
code
/* ID: yueqiq PROG: numtri LANG: C++ */ #include <set> #include <map> #include <ctime> #include <queue> #include <cmath> #include <stack> #include <limits> #include <vector> #include <bitset> #include <string> #include <cstdio> #include <cstring> #include <fstream> #include <string.h> #include <iostream> #include <algorithm> #define Si set<int> #define LL long long #define pb push_back #define PS printf(" ") #define Vi vector<int> #define LN printf("\n") #define lson l,m,rt << 1 #define rson m+1,r,rt<<1|1 #define SD(a) scanf("%d",&a) #define PD(a) printf("%d",a) #define SET(a,b) memset(a,b,sizeof(a)) #define FF(i,a) for(int i(0);i<(a);i++) #define FD(i,a) for(int i(a);i>=(1);i--) #define FOR(i,a,b) for(int i(a);i<=(b);i++) #define FOD(i,a,b) for(int i(a);i>=(b);i--) #define readf freopen("input.txt","r",stdin) #define writef freopen("output.txt","w",stdout) const int maxn = 102; const int INF = 0x3fffffff; const int dx[]={0,1,0,-1}; const int dy[]={1,0,-1,0}; const double pi = acos(-1.0); const double eps= 1e-7; using namespace std; //A=0,B=1,........ int N,M; int indegree[26]; bool link[26][26]; int path[26],cnt; int topsort(){ int zero_cnt=0; int zeronode; int in[26]; FF(i,26){ in[i]=indegree[i]; //printf(" i:%d in:%d\n",i,in[i]); } bool flag=false; cnt=0; SET(path,0); FF(i,N){ // puts("--------------------------"); // FF(j,N){ // printf(" i:%d in:%d\n",j,in[j]); // } // puts("--------------------------"); zero_cnt=0; FF(j,N){ if(in[j]==0){ zero_cnt++; zeronode=j; //PD(j);LN; } } //printf("zerocnt: %d zeronode:%d \n",zero_cnt,zeronode); if(zero_cnt==0) return -1;//loop occur; if(zero_cnt>1) flag=true;//ambigous in[zeronode]=-1; FF(j,N){ if(link[zeronode][j]) in[j]--; } path[cnt++]=zeronode; } if(flag) return 1; return 0; } int main() { char t[3]; int a,b; while(~scanf("%d%d",&N,&M)&&(N+M)){ SET(link,false);SET(indegree,0); int k=1,step=1; FOR(i,1,M){ scanf("%s",t); a=t[0]-'A'; b=t[2]-'A'; indegree[b]++; link[a][b]=true; if(k==1){ k=topsort(); step=i; } //PD(k);LN; } if(k==0){ printf("Sorted sequence determined after %d relations: ",step); FF(i,cnt){ printf("%c",(char)(path[i]+'A')); } puts("."); }else if(k==-1){ printf("Inconsistency found after %d relations.\n",step); }else{ puts("Sorted sequence cannot be determined."); } } return 0; }