POJ 2983 Is the Information Reliable?（差分约束#7）

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#include <cstdio>#include <algorithm>#include <cstdlib> #include <cstring>#define N 1010 #define M 1000000#define MAXQ  1000000using namespace std; const int inf = (-1u >> 1); int d[N], first[N];int u[M], v[M] , w[M], next[M]; bool inq[N];int cnt[N]; int e;int q[MAXQ];void addE(int x, int y, int c){      next[e] = first[x], first[x] = e;      u[e] = x, v[e] = y;      w[e] = c;       e++;}bool SPFA(int s, int n){       for (int i = 0; i <= n; i++)d[i] = inf;       memset(cnt, 0, sizeof(cnt));        d[s] = 0;       int qs, qe;        qs = qe = 0;        for (int i = 0; i <= n; i++)inq[i] = false;        q[qe++] = s;        while (qs != qe)       {              int x = q[qs];               inq[x] = false;              for (int e = first[x]; e != -1; e = next[e])if (d[v[e]] > d[u[e]] + w[e])              {                    d[v[e]] = d[u[e]] + w[e];                     if (!inq[v[e]])                    {                              inq[v[e]] = true;                              q[qe++] = v[e];                              if (qe == MAXQ)qe = 0;                               if (++cnt[v[e]] >n)return false;                     }              }              qs++;              if (qs == MAXQ)qs = 0;        }      return true; } int main(){      int n, m;     // FILE* fp = fopen("in.txt", "r");        while (scanf(  "%d", &n) != EOF)      {             scanf( "%d", &m);             int a, b, c;             char tt[3];              e = 0;              for (int i = 0; i <= n; i++)first[i] = -1;              for (int i = 0; i < m; i++)              {                   scanf( "%s %d %d", tt, &a, &b);                  if (tt[0] == 'V')                       addE(a, b, -1);                  else {                       scanf( "%d", &c);                       addE(b, a, c);                       addE(a, b, -c);                  }                  }             for (int i = 1; i <= n; i++)addE(0, i, 0);                                                 if (SPFA(0, n))puts("Reliable");              else puts("Unreliable");          //   getchar();getchar();       }      return 0;}