Solution URL
https://leetcode.com/submissions/detail/423810825/
代码
class Solution {
public void gameOfLife(int[][] board) {
//Ans: Solution
//Time: O(M * N)
//Space: O(M * N)
final int[][] directions = {
{-1, -1},
{-1, 0},
{-1, 1},
{0, -1},
{0, 1},
{1, -1},
{1, 0},
{1, 1}
};
int rows = board.length;
int cols = board[0].length;
int[][] board_copy = new int[rows][cols];
//copy the array
for(int i = 0; i < rows; i++){
for(int j = 0; j < cols; j++){
board_copy[i][j] = board[i][j];
}
}
//traverse the board, to count the number of 1 in all directions
//in order to decide whether the number will be live or die
for(int i = 0; i < rows; i++){
for(int j = 0; j < cols; j++){
//go to the eight directions of the current cell
int cnt = 0;
for(int[] dir: directions){
int r = i + dir[0];
int c = j + dir[1];
//check the bound
if(r >= 0 && r < rows && c >= 0 && c < cols){
//count the number of 1
if(board_copy[r][c] == 1) cnt++;
}
}
//follow the rule and update the cell
//rule 1 and 3
if((cnt < 2 || cnt > 3) && board[i][j] == 1) board[i][j] = 0;
//rule 2
if((cnt == 2 || cnt == 3) && board[i][j] == 1) board[i][j] = 1;
//rule 3
if(cnt == 3 && board[i][j] == 0) board[i][j] = 1;
}
}
}
}
