Method add_edge

code/graph/edmonds_karps.cpp:11–13

    memset(head = new int[n], -1, n*sizeof(int)); }
  void reset() { e = e_store; }
  void add_edge(int u, int v, int uv, int vu=0) {
    e.push_back(edge(v,uv,head[u])); head[u]=(int)size(e)-1;
    e.push_back(edge(u,vu,head[v])); head[v]=(int)size(e)-1;}
  int max_flow(int s, int t, bool res=true) {
    e_store = e;
    int l, r, v, f = 0;