Solution.go

type unionFind struct {
	p, size []int
}

func newUnionFind(n int) *unionFind {
	p := make([]int, n)
	size := make([]int, n)
	for i := range p {
		p[i] = i
		size[i] = 1
	}
	return &unionFind{p, size}
}

func (uf *unionFind) find(x int) int {
	if uf.p[x] != x {
		uf.p[x] = uf.find(uf.p[x])
	}
	return uf.p[x]
}

func (uf *unionFind) union(a, b int) bool {
	pa, pb := uf.find(a), uf.find(b)
	if pa == pb {
		return false
	}
	if uf.size[pa] > uf.size[pb] {
		uf.p[pb] = pa
		uf.size[pa] += uf.size[pb]
	} else {
		uf.p[pa] = pb
		uf.size[pb] += uf.size[pa]
	}
	return true
}

func (uf *unionFind) getSize(root int) int {
	return uf.size[root]
}

func minMalwareSpread(graph [][]int, initial []int) int {
	n := len(graph)
	s := make([]bool, n)
	for _, i := range initial {
		s[i] = true
	}
	uf := newUnionFind(n)
	for i := range graph {
		if !s[i] {
			for j := i + 1; j < n; j++ {
				if graph[i][j] == 1 && !s[j] {
					uf.union(i, j)
				}
			}
		}
	}
	g := make([]map[int]bool, n)
	for _, i := range initial {
		g[i] = map[int]bool{}
	}
	cnt := make([]int, n)
	for _, i := range initial {
		for j := 0; j < n; j++ {
			if !s[j] && graph[i][j] == 1 {
				g[i][uf.find(j)] = true
			}
		}
		for root := range g[i] {
			cnt[root]++
		}
	}
	ans, mx := 0, -1
	for _, i := range initial {
		t := 0
		for root := range g[i] {
			if cnt[root] == 1 {
				t += uf.getSize(root)
			}
		}
		if t > mx || t == mx && i < ans {
			ans, mx = i, t
		}
	}
	return ans
}