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c.go
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c.go
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package main
func maxDistance(grid [][]int) int {
n := len(grid)
type p struct{ i, j int }
lands := []p{}
vis := [100][100]bool{}
left := n * n
for i, g := range grid {
for j, c := range g {
if c == 1 {
lands = append(lands, p{i, j})
vis[i][j] = true
left--
}
}
}
if left == 0 || left == n*n {
return -1
}
dirOffset4 := [...][2]int{{1, 0}, {0, 1}, {-1, 0}, {0, -1}}
searchDirOffset4 := func(n, centerI, centerJ, dis int) {
for i, dir := range dirOffset4 {
dx := dirOffset4[(i+1)%4][0] - dir[0]
dy := dirOffset4[(i+1)%4][1] - dir[1]
x := centerI + dir[0]*dis
y := centerJ + dir[1]*dis
for _i := 0; _i < dis; _i++ {
if x >= 0 && x < n && y >= 0 && y < n {
if !vis[x][y] {
vis[x][y] = true
left--
}
}
x += dx
y += dy
}
}
}
ans := 1
for ; left > 0; ans++ {
for _, land := range lands {
searchDirOffset4(n, land.i, land.j, ans)
}
}
return ans - 1
}