Sorting It All Out

#include <bits/stdc++.h>
const int N=100000;
using namespace std;
vector<int>E[N];
int in[N],n,pos,flag,ok,m,sort1[N],stop,tmp[N];
char X,Y,O;
queue<int>q;
void init() {
    memset(in, 0, sizeof(in));
    for (int i = 0; i < n; i++) {
        E[i].clear();
    }
}

bool find(int u,int v) {
    for (int i = 0; i < E[u].size(); ++i)
        if (E[u][i] == v)
            return 1;
    return 0;
}

int toposort() {
    while (!q.empty()) {
        q.pop();
    }
    for (int i = 0; i < n; i++) {
        if (!in[i]) {
            q.push(i);
        }
    }
    pos = 0;
    bool f = 0;
    while (!q.empty()) {
        if (q.size() > 1) {
            f = 1;
        }
        int k = q.front();
        q.pop();
        sort1[pos++] = k;
        for (int i = 0; i < E[k].size(); i++) {
            if (--in[E[k][i]] == 0) {
                q.push(E[k][i]);
            }
        }
    }
    if (pos < n) return 1;
    if (f) return 2;
    return 3;
}


int main() {
    while (~scanf("%d%d%*c", &n, &m)) {
        if (n == 0 && m == 0) {
            break;
        }
        init();
        flag = 2;
        ok = 0;
        for (int i = 1; i <= m; i++) {
            scanf("%c%c%c%*c", &X, &O, &Y);
            if (ok) {
                continue;
            }
            int x = X - 'A', y = Y - 'A';
            if (O == '<' && !find(y, x)) {
                E[y].push_back(x);
                in[x]++;
            } else {
                if (O == '>' && !find(x, y)) {
                    E[x].push_back(y);
                    in[y]++;
                }
            }
            memcpy(tmp, in, sizeof(in));
            flag = toposort();
            memcpy(in, tmp, sizeof(in));
            if (flag != 2) {
                stop = i;
                ok = 1;
            }
        }
        if (flag == 3) {
            printf("Sorted sequence determined after %d relations: ", stop);
            for (int i = pos - 1; i >= 0; i--) {
                printf("%c", sort1[i] + 'A');
            }
            printf(".
");
        }
        if (flag == 1) {
            printf("Inconsistency found after %d relations.
", stop);
        }
        if (flag == 2) {
            printf("Sorted sequence cannot be determined.
");
        }
    }
}