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GameLife.swift
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GameLife.swift
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/**
* Question Link: https://leetcode.com/problems/game-of-life/
* Primary idea: Divide whole things to 4 cases, change 1 to 2 and 0 to 3 to avoid
* overrite issues, and then use %2 to get final results
*
* Time Complexity: O(n), Space Complexity: O(1)
*
*/
class GameLife {
func gameOfLife(_ board: inout [[Int]]) {
guard board.count > 0 else {
return
}
let m = board.count, n = board[0].count
for i in 0..<m {
for j in 0..<n {
changeStatus(&board, i, j, m, n)
}
}
board = board.map { $0.map { $0 % 2 } }
}
private func changeStatus(_ board: inout [[Int]], _ i: Int, _ j: Int, _ m: Int, _ n: Int) {
var liveNum = 0
for x in i - 1...i + 1 {
for y in j - 1...j + 1 {
if x < 0 || x >= m || y < 0 || y >= n {
continue
}
if x == i && y == j {
continue
}
liveNum = board[x][y] == 1 || board[x][y] == 2 ? liveNum + 1 : liveNum
}
}
if board[i][j] == 1 {
if liveNum < 2 || liveNum > 3 {
board[i][j] = 2
}
} else {
if liveNum == 3 {
board[i][j] = 3
}
}
}
}