#361 - Bomb Enemy

Medium • View on LeetCode • View on GitHub

Problem Description

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.

The bomb kills all the enemies in the same row and column from the planted point until it hits the wall since it is too strong to be destroyed.

Solution

/**
 * @param {character[][]} grid
 * @return {number}
 */
var maxKilledEnemies = function(grid) {
  const rows = grid.length;
  const cols = grid[0].length;
  const colHits = new Array(cols).fill(0);
  let rowHits = 0;
  let result = 0;

  for (let i = 0; i < rows; i++) {
    for (let j = 0; j < cols; j++) {
      if (j === 0 || grid[i][j-1] === 'W') {
        rowHits = 0;
        for (let k = j; k < cols && grid[i][k] !== 'W'; k++) {
          if (grid[i][k] === 'E') rowHits++;
        }
      }
      if (i === 0 || grid[i-1][j] === 'W') {
        colHits[j] = 0;
        for (let k = i; k < rows && grid[k][j] !== 'W'; k++) {
          if (grid[k][j] === 'E') colHits[j]++;
        }
      }
      if (grid[i][j] === '0') {
        result = Math.max(result, rowHits + colHits[j]);
      }
    }
  }

  return result;
};