Solution.ts

/**
 Do not return anything, modify board in-place instead.
 */
function gameOfLife(board: number[][]): void {
    const m = board.length;
    const n = board[0].length;
    for (let i = 0; i < m; ++i) {
        for (let j = 0; j < n; ++j) {
            let live = -board[i][j];
            for (let x = i - 1; x <= i + 1; ++x) {
                for (let y = j - 1; y <= j + 1; ++y) {
                    if (x >= 0 && x < m && y >= 0 && y < n && board[x][y] > 0) {
                        ++live;
                    }
                }
            }
            if (board[i][j] === 1 && (live < 2 || live > 3)) {
                board[i][j] = 2;
            }
            if (board[i][j] === 0 && live === 3) {
                board[i][j] = -1;
            }
        }
    }
    for (let i = 0; i < m; ++i) {
        for (let j = 0; j < n; ++j) {
            if (board[i][j] === 2) {
                board[i][j] = 0;
            }
            if (board[i][j] === -1) {
                board[i][j] = 1;
            }
        }
    }
}