Sorting It All Out
Time Limit:1000MS Memory Limit:10000KB 64bit IO Format:%lld & %llu
Description
An ascending sorted sequence of distinct values is one in which some form of a less-than operator is used to order the elements from smallest to largest. For example, the sorted sequence A, B, C, D implies that A < B, B < C and C < D. in this problem, we will give you a set of relations of the form A < B and ask you to determine whether a sorted order has been specified or not.
Input
Input consists of multiple problem instances. Each instance starts with a line containing two positive integers n and m. the first value indicated the number of objects to sort, where 2 <= n <= 26. The objects to be sorted will be the first n characters of the uppercase alphabet. The second value m indicates the number of relations of the form A < B which will be given in this problem instance. Next will be m lines, each containing one such relation consisting of three characters: an uppercase letter, the character "<" and a second uppercase letter. No letter will be outside the range of the first n letters of the alphabet. Values of n = m = 0 indicate end of input.
Output
For each problem instance, output consists of one line. This line should be one of the following three:
Sorted sequence determined after xxx relations: yyy...y.
Sorted sequence cannot be determined.
Inconsistency found after xxx relations.
where xxx is the number of relations processed at the time either a sorted sequence is determined or an inconsistency is found, whichever comes first, and yyy...y is the sorted, ascending sequence.
Sample Input
4 6 A<B A<C B<C C<D B<D A<B 3 2 A<B B<A 26 1 A<Z 0 0
Sample Output
Sorted sequence determined after 4 relations: ABCD. Inconsistency found after 2 relations. Sorted sequence cannot be determined. 套模板硬上
#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <queue>
#include <vector>
#include <iomanip>
#include <math.h>
#include <map>
using namespace std;
#define FIN freopen("input.txt","r",stdin);
#define FOUT freopen("output.txt","w",stdout);
#define INF 0x3f3f3f3f
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
typedef long long LL;
const int MAXN=1e5+5;
struct Edge{
int v,nxt;
}E[MAXN*2];
int Head[MAXN],erear;
int IN[MAXN],P[MAXN],sz;
int temp[MAXN];
int n,m,sum;
int flag,ed;
bool con;
void edge_init(){
erear=0;
memset(Head,-1,sizeof(Head));
memset(IN,0,sizeof(IN));
sum=0;
con=0;
}
void edge_add(int u,int v){
E[erear].v=v;
E[erear].nxt=Head[u];
Head[u]=erear++;
}
int topsort(){
sz=0;
queue<int>Q;
for(int i=0;i<n;i++){
if(!IN[i]) Q.push(i);
}
bool sign=0;
while(!Q.empty()){
if(Q.size()>=2) sign=1;
int u=Q.front();
Q.pop();
P[sz++]=u;
for(int i=Head[u];~i;i=E[i].nxt){
int v=E[i].v;
IN[v]--;
if(!IN[v]) Q.push(v);
}
}
if(sz<n){
//printf("invalid\n");
return 1;
}else if(sign){
//printf("multi ans\n");
return 2;
}else{
return 3;
}
/*for(int i=0;i<sz;i++){
if(i==0) printf("%d",P[i]);
else printf(" %d",P[i]);
}
printf("\n");*/
}
int main()
{
//FIN
while(~scanf("%d%d",&n,&m))
{
if(n==0&&m==0) break;
edge_init();
flag=2;
char op[10];
for(int i=1;i<=m;i++){
scanf("%s",op);
if(con) continue;
int u=(int)op[0]-‘A‘;
int v=(int)op[2]-‘A‘;
if(op[1]==‘>‘){
edge_add(u,v);
IN[v]++;
}
else{
edge_add(v,u);
IN[u]++;
}
memcpy(temp,IN,sizeof(IN));
flag=topsort();
memcpy(IN,temp,sizeof(temp));
sum=i;
if(flag!=2){
ed=i;
con=true;
}
}
if(flag==3){
printf("Sorted sequence determined after %d relations: ", ed);
for(int i=sz-1; i>=0; --i)
printf("%c",P[i]+‘A‘);
printf(".\n");
}
else if(flag==1){
printf("Inconsistency found after %d relations.\n",ed);
}
else{
printf("Sorted sequence cannot be determined.\n");
}
}
return 0;
}