How hard is LeetCode 361. Bomb Enemy?

LeetCode 361. Bomb Enemy is rated Medium on LeetCode.

What topics does LeetCode 361. Bomb Enemy cover?

LeetCode 361. Bomb Enemy is tagged Array, Dynamic Programming and Matrix on LeetCode.

Is LeetCode 361. Bomb Enemy a premium problem?

Yes. LeetCode 361. Bomb Enemy is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.

Bomb Enemy — LeetCode 361 Python Solution

MediumLeetCode PremiumArrayDynamic ProgrammingMatrix

Problem: #361
Pattern: Matrix and Grid
Reading time: 7 min
Source: leetcode.com

The problem

Given an m x n matrix grid where each cell is either a wall 'W', an enemy 'E' or empty '0', return the maximum enemies you can kill using one bomb. You can only place the bomb in an empty cell.

Example

Input: grid = [["0","E","0","0"],["E","0","W","E"],["0","E","0","0"]]
Output: 3

Python solution

Python

class Solution:
    def maxKilledEnemies(self, grid: List[List[str]]) -> int:
        m, n = len(grid), len(grid[0])
        g = [[0] * n for _ in range(m)]
        for i in range(m):
            t = 0
            for j in range(n):
                if grid[i][j] == 'W':
                    t = 0
                elif grid[i][j] == 'E':
                    t += 1
                g[i][j] += t
            t = 0
            for j in range(n - 1, -1, -1):
                if grid[i][j] == 'W':
                    t = 0
                elif grid[i][j] == 'E':
                    t += 1
                g[i][j] += t
        for j in range(n):
            t = 0
            for i in range(m):
                if grid[i][j] == 'W':
                    t = 0
                elif grid[i][j] == 'E':
                    t += 1
                g[i][j] += t
            t = 0
            for i in range(m - 1, -1, -1):
                if grid[i][j] == 'W':
                    t = 0
                elif grid[i][j] == 'E':
                    t += 1
                g[i][j] += t
        return max(
            [g[i][j] for i in range(m) for j in range(n) if grid[i][j] == '0'],
            default=0,
        )

Complexity

Measure	Complexity
Time	O(n·m) (typical)
Space	O(n·m) or optimized auxiliary

Pattern: Matrix and Grid

Treat a 2-D grid as a graph whose neighbours are the four adjacent cells. LeetCode 361. Bomb Enemy is filed here because LeetCode tags it Matrix, which is the vocabulary this hub collects.

The matrix and grid guide has the Python template for the pattern and the 216 LeetCode problems that use it.

Frequently asked questions

How hard is LeetCode 361. Bomb Enemy?: LeetCode 361. Bomb Enemy is rated Medium on LeetCode.
What topics does LeetCode 361. Bomb Enemy cover?: LeetCode 361. Bomb Enemy is tagged Array, Dynamic Programming and Matrix on LeetCode.
Is LeetCode 361. Bomb Enemy a premium problem?: Yes. LeetCode 361. Bomb Enemy is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.