Bomb Enemy

Problem: Bomb Enemy

Try to scan all possible enemies at starting empty position horizontally and vertically of one free block. Also only count of one previous row is necessary to be stored to save memory.

Code in Python:

class Solution(object):
    def maxKilledEnemies(self, grid):
        """
        :type grid: List[List[str]]
        :rtype: int
        """
        if len(grid) == 0 or len(grid[0]) == 0: return 0

        rows, cols = len(grid), len(grid[0])

        res = 0
        row = [[0, 0] for _ in xrange(cols)]
        prev_row = []

        for i in xrange(rows):
            for j in xrange(cols):
                if grid[i][j] == "W":
                    continue

                if j == 0 or grid[i][j-1] == "W":
                    count, _j = 0, j
                    while _j < cols and grid[i][_j] != "W":
                        if grid[i][_j] == "E": count += 1
                        _j += 1
                    row[j][0] = count
                else:
                    row[j][0] = row[j-1][0]

                if i == 0 or grid[i-1][j] == "W":
                    count, _i = 0, i
                    while _i < rows and grid[_i][j] != "W":
                        if grid[_i][j] == "E": count += 1
                        _i += 1
                    row[j][1] = count
                else:
                    row[j][1] = prev_row[j][1]

                if grid[i][j] != "E": res = max(res, sum(row[j]))
                prev_row = row

        return res