题目大意：判断一个序列是否可图化。Havel-Hakimi定理的简单应用。

　　在看的关于时提到这道题，就做了一下。可悲的是，因为一些小细节问题WA了两次，无语...

1 #include 
      
        2 #include 
       
         3 #include 
        
          4 using namespace std; 5 #define MAXN 12 6  7 struct Vertex 8 { 9     int d, id;10     bool operator < (const Vertex& v) const11     {12         return d > v.d;13     }14 };15 Vertex vertex[MAXN];16 int G[MAXN][MAXN], n;17 18 bool Havel_Hakimi()19 {20     for (int i = 0; i < n-1; i++)21     {22         sort(vertex+i, vertex+n);23         if (i + vertex[i].d >= n)  return false;24         int x = vertex[i].id;25         for (int j = i+1; j <= i+vertex[i].d; j++)26         {27             vertex[j].d--;28             int y = vertex[j].id;29             G[x][y] = G[y][x] = 1;30             if (vertex[j].d < 0)  return false;31         }32     }33     if (vertex[n-1].d)  return false;34     return true;35 }36 37 int main()38 {39 #ifdef LOCAL40     freopen("in", "r", stdin);41 #endif42     int T;43     scanf("%d", &T);44     while (T--)45     {46         scanf("%d", &n);47         for (int i = 0; i < n; i++)48         {49             scanf("%d", &vertex[i].d);50             vertex[i].id = i;51         }52         memset(G, 0, sizeof(G));53         if (Havel_Hakimi())  54         {55             printf("YES\n");56             for (int i = 0; i < n; i++)57                 for (int j = 0; j < n; j++)58                     printf("%d%s", G[i][j], (j == n-1) ? "\n" : " ");59         }60         else  printf("NO\n");61         if (T)  printf("\n");62     }63     return 0;64 }