[Leetcode] [JavaScript] Game of Life

Game of Life

According to the Wikipedia's article: "The Game of Life, also known simply as Life, was a cellular automaton devised by the British mathematician John Horton Conway in 1970. "

Given a board with m - n cells, each cell have an initial state live (1) or dead (0). Each cell interacts with its eight neighbors (horizontal, vertical, diagonal) using the following four rules (taken from t He above Wikipedia article):

1. Any live cell with fewer than-live neighbors dies, as if caused by under-population.
2. Any live cell with a or three live neighbors lives on to the next generation.
3. Any live cell with more than three live neighbors dies, as if by over-population.
4. Any dead cells with exactly three live neighbors becomes a live cell, as if by reproduction.

Write a function to compute the next state (after one update) of the board given it current state.

Follow up:

1. Could You solve it in-place? Remember the board needs to be updated at the same time:you cannot update some cells first and then use their update D values to update the other cells.
2. In this question, we represent the board using a 2D array. In principle, the board was infinite, which would cause problems when the active area encroaches the border of the array. How would address these problems?

Game of life, requires in-place, that is, only in the board array, do not open extra array space.

Tidy up the rules:

1. A neighbor less than 2 or more than 3 will die;

2. The neighbor equals 2, the state is unchanged, what is the original or what;

3. The neighbor equals 3, survives, regardless of the original state.

In-place mainly need to solve a problem, when dealing with a cell, can not be judged according to the state after the change, according to the original state.

The first round of processing is nothing more than 4 cases: 0, 0, 1, 1, 0, 1, 1, 0.

0--0, 1--1 No problem, we put 0--1 into 2, 1--0 to 3.

1 and 3 are considered to be alive when judging neighbors.

The second cycle turns all 2 into 1 and 3 to 0.

1 /**2 * @param {number[][]} board3 * @return {void} does not return anything, modify board In-place instead.4  */5 varGameoflife =function(board) {6     varI, J;7      for(i = 0; i < board.length; i++){8          for(j = 0; J < Board[i].length; J + +){9             varCurr =Board[i][j];Ten             varNeighbors =Countneighbors (i, j); One             if(Neighbors < 2 | | Neighbors > 3){ A                 if(Curr = = 1){ -BOARD[I][J] = 3; -                 } the}Else if(Neighbors = = 3){ -                 if(Curr = = 0){ -BOARD[I][J] = 2; -                 } +             } -         } +     } A      for(i = 0; i < board.length; i++){ at          for(j = 0; J < Board[i].length; J + +){ -             if(Board[i][j] = = = 2){ -BOARD[I][J] = 1; -}Else if(Board[i][j] = = = 3){ -BOARD[I][J] = 0; -             } in         } -     } to  +  -     functionCountneighbors (i, j) { the         varCount = 0; *Count + = isAlive (i, j-1); Count + = IsAlive (i, j + 1); $Count + = isAlive (i-1, j-1); Count + = IsAlive (I-1, J); Count + = IsAlive (i-1, J + 1);Panax NotoginsengCount + = isAlive (i + 1, j-1); Count + = isAlive (i + 1, j); Count + = isAlive (i + 1, j + 1); -         returncount; the     } +     functionisAlive (i, j) { A         if(!board[i] | |!Board[i][j]) { the             return0; +         } -         varCell =Board[i][j]; $         if(cell = = = 1 | | cell = = = 3){ $             return1; -         } -         return0; the     } -};

[Leetcode] [JavaScript] Game of Life