Merge pull request soapyigu#368 from soapyigu/Array

Array

Author: soapyigu

Array/BombEnemy.swift

@@ -0,0 +1,50 @@
+/**
+ * Question Link: https://leetcode.com/problems/bomb-enemy/
+ * Primary idea: Greedy. Update the result only when there is wall or at the beginning.
+ * Time Complexity: O(mn), Space Complexity: O(n)
+ *
+ */
+
+class BombEnemy {
+    func maxKilledEnemies(_ grid: [[Character]]) -> Int {
+        let m = grid.count, n = grid[0].count
+        var res = 0, rowHit = 0, colHit = Array(repeating: 0, count: n)
+
+        for i in 0..<m {
+            for j in 0..<n {
+
+                // check row
+                if j == 0 || grid[i][j - 1] == "W" {
+                    rowHit = 0
+                    for y in j..<n {
+                        if grid[i][y] == "W" {
+                            break
+                        }
+                        if grid[i][y] == "E" {
+                            rowHit += 1
+                        }
+                    }
+                }
+
+                // check col
+                if i == 0 || grid[i - 1][j] == "W" {
+                    colHit[j] = 0
+                    for x in i..<m {
+                        if grid[x][j] == "W" {
+                            break
+                        }
+                        if grid[x][j] == "E" {
+                            colHit[j] += 1
+                        }
+                    }
+                }
+            
+                if grid[i][j] == "0" {
+                    res = max(res, rowHit + colHit[j])
+                }
+            }
+        }
+
+        return res
+    }
+}

Array/SquaresSortedArray.swift

@@ -0,0 +1,29 @@
+/**
+ * Question Link: https://leetcode.com/problems/squares-of-a-sorted-array/
+ * Primary idea: Two pointers. Compare absolute value and assign the bigger one to the right most index of the result.
+ * Time Complexity: O(n), Space Complexity: O(1)
+ *
+ */
+
+class SquaresSortedArray {
+    func sortedSquares(_ nums: [Int]) -> [Int] {
+        var left = 0, right = nums.count - 1, res = Array(repeating: 0, count: nums.count)
+        var square = 0, idx = nums.count - 1
+
+        while left <= right {
+            
+            if abs(nums[left]) < abs(nums[right]) {
+                square = nums[right]
+                right -= 1
+            } else {
+                square = nums[left]
+                left += 1
+            }
+
+            res[idx] = square * square
+            idx -= 1
+        }
+
+        return res
+    }
+}