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| // @Title: 飞地的数量 (Number of Enclaves)
// @Author: 15816537946@163.com
// @Date: 2022-02-12 16:23:40
// @Runtime: 64 ms
// @Memory: 7.2 MB
type unionFind struct {
parent []int
rank []int
onEdge []bool
}
func newUnionFind(grid [][]int) unionFind {
m,n := len(grid), len(grid[0])
parent := make([]int, m*n)
rank := make([]int, m*n)
onEdge := make([]bool, m*n)
for i, row := range grid {
for j, v := range row {
if v == 1 {
idx := i*n+j
parent[idx] = idx
if i ==0 || i == m-1 || j ==0 || j == n-1 {
onEdge[idx] = true
}
}
}
}
return unionFind{parent,rank, onEdge}
}
func (uf unionFind) find(x int) int {
if uf.parent[x] != x {
uf.parent[x] = uf.find(uf.parent[x])
}
return uf.parent[x]
}
func (uf unionFind) merge(x,y int) {
x,y = uf.find(x), uf.find(y)
if x == y {
return
}
if uf.rank[x] > uf.rank[y] {
uf.parent[y] = x
uf.onEdge[x] = uf.onEdge[x] || uf.onEdge[y]
} else if uf.rank[x] < uf.rank[y] {
uf.parent[x] = y
uf.onEdge[y] = uf.onEdge[y] || uf.onEdge[x]
} else {
uf.parent[y] = x
uf.onEdge[x] = uf.onEdge[x] || uf.onEdge[y]
uf.rank[x]++
}
}
func numEnclaves(grid [][]int) (ans int) {
uf := newUnionFind(grid)
m,n := len(grid), len(grid[0])
for i, row := range grid {
for j,v := range row {
if v == 1 {
idx := i *n +j
if j+1<n && grid[i][j+1] == 1 {
uf.merge(idx, idx+1)
}
if i+1 <m && grid[i+1][j] == 1 {
uf.merge(idx, idx+n)
}
}
}
}
for i :=1;i<m-1;i++ {
for j :=1;j<n-1;j++ {
if grid[i][j] == 1 && !uf.onEdge[uf.find(i*n+j)] {
ans++
}
}
}
return
}
|