package main

type (
	AdjacencyMatrix map[int]map[int]int

	Graph struct {
		X map[int]Vector
		A AdjacencyMatrix
	}
)

func (A AdjacencyMatrix) Modify(u, v, w int) {
	if A[u] == nil {
		A[u] = make(map[int]int)
	}
	A[u][v] = w
}

func MakeGraph() Graph {
	return Graph{make(map[int]Vector), make(AdjacencyMatrix)}
}

func (G Graph) AddNode(u int, V Vector) {
	G.X[u] = V
}

func (G Graph) AddEdge(u, v int) {
	G.A.Modify(u, v, 1)
	G.A.Modify(v, u, -1)
}