README.md

361. 轰炸敌人

English Version

题目描述

给你一个大小为 m x n 的矩阵 grid ，其中每个单元格都放置有一个字符：

• 'W' 表示一堵墙
• 'E' 表示一个敌人
• '0'（数字 0）表示一个空位

返回你使用 一颗炸弹 可以击杀的最大敌人数目。你只能把炸弹放在一个空位里。

由于炸弹的威力不足以穿透墙体，炸弹只能击杀同一行和同一列没被墙体挡住的敌人。

 

示例 1：

输入：grid = [["0","E","0","0"],["E","0","W","E"],["0","E","0","0"]]
输出：3

示例 2：

输入：grid = [["W","W","W"],["0","0","0"],["E","E","E"]]
输出：1

 

提示：

• m == grid.length
• n == grid[i].length
• 1 <= m, n <= 500
• grid[i][j] 可以是 'W'、'E' 或 '0'

解法

Python3

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,
        )

Java

class Solution {
    public int maxKilledEnemies(char[][] grid) {
        int m = grid.length;
        int n = grid[0].length;
        int[][] g = new int[m][n];
        for (int i = 0; i < m; ++i) {
            int t = 0;
            for (int j = 0; j < n; ++j) {
                if (grid[i][j] == 'W') {
                    t = 0;
                } else if (grid[i][j] == 'E') {
                    ++t;
                }
                g[i][j] += t;
            }
            t = 0;
            for (int j = n - 1; j >= 0; --j) {
                if (grid[i][j] == 'W') {
                    t = 0;
                } else if (grid[i][j] == 'E') {
                    ++t;
                }
                g[i][j] += t;
            }
        }
        for (int j = 0; j < n; ++j) {
            int t = 0;
            for (int i = 0; i < m; ++i) {
                if (grid[i][j] == 'W') {
                    t = 0;
                } else if (grid[i][j] == 'E') {
                    ++t;
                }
                g[i][j] += t;
            }
            t = 0;
            for (int i = m - 1; i >= 0; --i) {
                if (grid[i][j] == 'W') {
                    t = 0;
                } else if (grid[i][j] == 'E') {
                    ++t;
                }
                g[i][j] += t;
            }
        }
        int ans = 0;
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                if (grid[i][j] == '0') {
                    ans = Math.max(ans, g[i][j]);
                }
            }
        }
        return ans;
    }
}

C++

class Solution {
public:
    int maxKilledEnemies(vector<vector<char>>& grid) {
        int m = grid.size(), n = grid[0].size();
        vector<vector<int>> g(m, vector<int>(n));
        for (int i = 0; i < m; ++i) {
            int t = 0;
            for (int j = 0; j < n; ++j) {
                if (grid[i][j] == 'W')
                    t = 0;
                else if (grid[i][j] == 'E')
                    ++t;
                g[i][j] += t;
            }
            t = 0;
            for (int j = n - 1; j >= 0; --j) {
                if (grid[i][j] == 'W')
                    t = 0;
                else if (grid[i][j] == 'E')
                    ++t;
                g[i][j] += t;
            }
        }
        for (int j = 0; j < n; ++j) {
            int t = 0;
            for (int i = 0; i < m; ++i) {
                if (grid[i][j] == 'W')
                    t = 0;
                else if (grid[i][j] == 'E')
                    ++t;
                g[i][j] += t;
            }
            t = 0;
            for (int i = m - 1; i >= 0; --i) {
                if (grid[i][j] == 'W')
                    t = 0;
                else if (grid[i][j] == 'E')
                    ++t;
                g[i][j] += t;
            }
        }
        int ans = 0;
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                if (grid[i][j] == '0') ans = max(ans, g[i][j]);
            }
        }
        return ans;
    }
};

Go

func maxKilledEnemies(grid [][]byte) int {
	m, n := len(grid), len(grid[0])
	g := make([][]int, m)
	for i := range g {
		g[i] = make([]int, n)
	}
	for i := 0; i < m; i++ {
		t := 0
		for j := 0; j < n; j++ {
			if grid[i][j] == 'W' {
				t = 0
			} else if grid[i][j] == 'E' {
				t++
			}
			g[i][j] += t
		}
		t = 0
		for j := n - 1; j >= 0; j-- {
			if grid[i][j] == 'W' {
				t = 0
			} else if grid[i][j] == 'E' {
				t++
			}
			g[i][j] += t
		}
	}
	for j := 0; j < n; j++ {
		t := 0
		for i := 0; i < m; i++ {
			if grid[i][j] == 'W' {
				t = 0
			} else if grid[i][j] == 'E' {
				t++
			}
			g[i][j] += t
		}
		t = 0
		for i := m - 1; i >= 0; i-- {
			if grid[i][j] == 'W' {
				t = 0
			} else if grid[i][j] == 'E' {
				t++
			}
			g[i][j] += t
		}
	}
	ans := 0
	for i, row := range grid {
		for j, v := range row {
			if v == '0' && ans < g[i][j] {
				ans = g[i][j]
			}
		}
	}
	return ans
}

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