View Compilation Error

0_0_36756086_26337.cpp:10:28: error: 'acos' was not declared in this scope
 const double PI = acos(-1.0); 
                            ^
0_0_36756086_26337.cpp: In function 'void dfs(int)':
0_0_36756086_26337.cpp:21:30: error: 'memset' was not declared in this scope
  memset(f[u], 0, sizeof(f[u])); // 如果是叶子节点，并且花费为0时，要变成1
                              ^
0_0_36756086_26337.cpp: In function 'int main()':
0_0_36756086_26337.cpp:52:29: error: 'memset' was not declared in this scope
   memset(vis, 0, sizeof(vis)); 
                             ^