POJ 3169 Layout （差分约束#5）

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当d[n] = inf 时即输出 -2；
#include <cstdio>#include <algorithm>#include <cstdlib> #include <cstring>#define N 1010 #define M 35000#define MAXQ  35000using namespace std; const int inf = (-1u >> 1); int d[N], first[N];int v[M] , w[M], next[M]; bool inq[N];int cnt[N]; int e;int q[MAXQ];int indx[N]; int t[N]; void addE(int x, int y, int c){      next[e] = first[x], first[x] = e;      v[e] = y;      w[e] = c;       e++;}int SPFA(int s, int n){       for (int i = 1; i <= n; i++)d[i] = inf;       memset(cnt, 0, sizeof(cnt));        d[s] = 0;       int qs, qe;        qs = qe = 0;        for (int i = 1; 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[x] + w[e])              {                    d[v[e]] = d[x] + 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 -1;                     }              }              qs++;              if (qs == MAXQ)qs = 0;        }       if (d[n] == inf)return -2;       return d[n]; } int main(){      int n, ml, md;      int A, B, D;     // FILE* fp = fopen("in.txt", "r");       scanf( "%d %d %d", &n, &ml, &md);      for (int i = 0; i <= n; i++) first[i] = -1;       while (ml--)      {            scanf( "%d %d %d", &A, &B, &D);            if (A > B)A ^= B, B^= A, A ^= B;            addE(A, B, D);      }      while (md--)      {             scanf( "%d %d %d", &A, &B, &D);             if (A > B)A ^= B, B^= A, A ^= B;             addE(B, A, -D);      }      printf("%d\n", SPFA(1, n));      //getchar();}