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| // @Title: 水位上升的泳池中游泳 (Swim in Rising Water)
// @Author: 15816537946@163.com
// @Date: 2021-01-30 09:59:24
// @Runtime: 8 ms
// @Memory: 4.4 MB
type unionFind struct {
parent, size []int
}
func newUnionFind(n int) *unionFind {
parent := make([]int, n)
size := make([]int, n)
for i := range parent {
parent[i] = i
size[i] = 1
}
return &unionFind{parent, size}
}
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) union(x, y int) {
fx, fy := uf.find(x), uf.find(y)
if fx == fy {
return
}
if uf.size[fx] < uf.size[fy] {
fx, fy = fy, fx
}
uf.size[fx] += uf.size[fy]
uf.parent[fy] = fx
}
func (uf *unionFind) inSameSet(x, y int) bool {
return uf.find(x) == uf.find(y)
}
type pair struct{ x, y int }
var dirs = []pair{{-1, 0}, {1, 0}, {0, -1}, {0, 1}}
func swimInWater(grid [][]int) (ans int) {
n := len(grid)
pos := make([]pair, n*n)
for i, row := range grid {
for j, h := range row {
pos[h] = pair{i, j} // 存储每个平台高度对应的位置
}
}
uf := newUnionFind(n * n)
for threshold := 0; ; threshold++ {
p := pos[threshold]
for _, d := range dirs {
if x, y := p.x+d.x, p.y+d.y; 0 <= x && x < n && 0 <= y && y < n && grid[x][y] <= threshold {
uf.union(x*n+y, p.x*n+p.y)
}
}
if uf.inSameSet(0, n*n-1) {
return threshold
}
}
}
|