add new solutions

solutions/2/q289/solution.go

@@ -0,0 +1,41 @@
+package q289
+
+func countLiveNeighbors(board [][]int, row, col int) int {
+	cnt := 0
+	for r := row - 1; r <= row+1; r++ {
+		for c := col - 1; c <= col+1; c++ {
+			if r == row && c == col || r < 0 || c < 0 || r >= len(board) || c >= len(board[0]) {
+				continue
+			}
+			cnt += board[r][c] & 1
+		}
+	}
+	return cnt
+}
+
+func gameOfLife(board [][]int) {
+	for r := range board {
+		for c := range board[r] {
+			neighbors := countLiveNeighbors(board, r, c)
+			if board[r][c]&1 == 1 {
+				switch {
+				case neighbors < 2 || neighbors > 3:
+					// die
+				default:
+					board[r][c] |= 2 // survive
+				}
+			} else if neighbors == 3 {
+				board[r][c] |= 2 // birth
+			}
+		}
+	}
+
+	// Next generation
+	for r := range board {
+		for c := range board[r] {
+			board[r][c] >>= 1
+		}
+	}
+}
+
+var _ = gameOfLife