[leetcode]Game of life

用bit去记current和future

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public class Solution { public void gameOfLife(int[][] board) { for (int i = 0; i < board.length; i++){ for (int j = 0; j < board[i].length; j++){ board[i][j] |= (nextState(board, i, j) << 1); } } for (int i = 0; i < board.length; i++){ for (int j = 0; j < board[i].length; j++){ board[i][j] = futureBit(board[i][j]); } } } private int nextState(int [][]board, int i, int j){ int live = currentBit(board[i][j]); int up = i == 0?0:currentBit(board[i-1][j]); int down = i == board.length-1?0:currentBit(board[i+1][j]); int left = j == 0?0:currentBit(board[i][j-1]); int right = j == board[i].length-1?0:currentBit(board[i][j+1]); int upLeft = (i==0 || j==0)?0:currentBit(board[i-1][j-1]); int upRight = (i == 0||j==board[i].length-1)?0:currentBit(board[i-1][j+1]); int downLeft = (i == board.length-1||j==0)?0:currentBit(board[i+1][j-1]); int downRight = (i == board.length-1||j==board[i].length-1)?0:currentBit(board[i+1][j+1]); int totalLive = up+down+left+right+upLeft+upRight+downLeft+downRight; if (live == 1){ if (totalLive < 2) return 0; if (totalLive > 3) return 0; return 1; } return totalLive == 3?1:0; } private int futureBit(int num){ return (num&0x2) >> 1; } private int currentBit(int num){ return (num&0x1); } }