poj 1094 Sorting It All Out（拓扑排序）

Sorting It All Out

Time Limit: 1000MS Memory Limit: 10000KTotal Submissions: 28762 Accepted: 9964

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 6A<BA<CB<CC<DB<DA<B3 2A<BB<A26 1A<Z0 0

Sample Output

Sorted sequence determined after 4 relations: ABCD.Inconsistency found after 2 relations.Sorted sequence cannot be determined.

Source Code
#include<iostream>#include<algorithm>#include<stdio.h>#include<string.h>#include<stdlib.h>using namespace std;int num[201];int n,m;int map[301][301];int v[301];int count1;int a[301];int TP1(){    int pcount = count1;    int cnt = 0;    int pm[301];    memset(pm,0,sizeof(pm));    for(int pa='A'; pa<='Z'; pa++)    {        pm[pa] = 0;        pm[pa] = num[pa];    }    for(int pa=0; pa<n; pa++)    {        int f1 = 0;        for(int pb='A'; pb<='Z'; pb++)        {            if(pm[pb] == 0 && v[pb])            {                f1 = 1;                pm[pb]--;                pcount--;                for(int pc='A'; pc<='Z'; pc++)                {                    if(map[pc][pb] == 1)                    {                        pm[pc]--;                    }                }                break;            }        }        if(f1 == 0 && pcount)        {            return 0;        }    }    return 1;}int TP(){    memset(a,0,sizeof(a));    int pn = 0;    int mm[201];    int cnt = 0;    for(int pi='A'; pi<='Z'; pi++)    {        mm[pi] = 0;        mm[pi] = num[pi];    }    for(int pi='A'; pi<='Z'; pi++)    {        if(mm[pi] == 0 && v[pi])        {            cnt++;        }    }    if(cnt>1)    {        return 0;    }    if(cnt == 0)    {        return -1;    }    for(int pi=0; pi<n; pi++)    {        for(int pj='A'; pj<='Z'; pj++)        {            if(mm[pj] == 0 && v[pj])            {                a[pn++] = pj;                mm[pj]--;                count1--;                cnt = 0;                for(int pk='A'; pk<='Z'; pk++)                {                    if(map[pk][pj] == 1)                    {                        mm[pk]--;                        if(mm[pk] == 0)                        {                            cnt++;                        }                    }                }                               if(cnt>1)                {                    return 0;                }                if(cnt == 0 && count1)                {                                        return -1;                }                break;            }        }    }       if(count1 == 0 && pn == n)    {        return 1;    }    else if(count1 == 0 && pn!=n)    {        return 0;    }    else    {        return -1;    }}int b[30];int main(){    while(scanf("%d%d",&n,&m)!=EOF)    {        if(n == 0 && m == 0)        {            break;        }        int pf = 0,flag = 0,pi1;        memset(b,0,sizeof(b));        char str[10];        memset(num,0,sizeof(num));        memset(v,0,sizeof(v));        memset(map,0,sizeof(map));        for(int i=0; i<m; i++)        {            scanf("%s",str);            if(map[str[0]][str[2]] == 0)            {                num[str[0]]++;                v[str[0]]++;                v[str[2]]++;                map[str[0]][str[2]] = 1;            }            count1 = 0;            for(int j='A'; j<='Z'; j++)            {                if(v[j])                {                    count1++;                }            }            int pk;            if(flag!=1)            {                if(TP1() && pf == 0)                {                    pk = TP();                    if(pf == 0)                    {                        if(pk == -1)                        {                            pf = 1;                            flag = 2;                            pi1 = i+1;                        }                        else if(pk == 1 && flag == 0)                        {                            flag = 1;                            pi1 = i+1;                            for(int l=0; l<n; l++)                            {                                b[l] = a[l];                            }                        }                    }                }                else                {                    if(pf == 0)                    {                        pi1 = i+1;                        flag = 2;                        pf = 1;                    }                }            }        }        if(flag == 0)        {            printf("Sorted sequence cannot be determined.\n");        }        else if(flag == 1)        {            printf("Sorted sequence determined after %d relations: ",pi1);            for(int pj=n-1; pj>=0; pj--)            {                printf("%c",b[pj]);            }            printf(".\n");        }        else if(flag == 2)        {            printf("Inconsistency found after %d relations.\n",pi1);        }    }    return 0;}