Merge pull request #350 from soapyigu/Design

Design

Author: soapyigu

Design/DetectSquares.swift

@@ -0,0 +1,60 @@
+/**
+ * Question Link: https://leetcode.com/problems/detect-squares/
+ * Primary idea: Use hashmap to track points having the same x and y and calculate all possible results
+ *
+ * Time Complexity: add - O(1), count - O(n)
+ * Space Complexity: O(n)
+ *
+ */
+
+class DetectSquares {
+    
+    private var xPoints = [Int: [Int: Int]]()
+    private var yPoints = [Int: [Int: Int]]()
+
+    init() { }
+    
+    func add(_ point: [Int]) {
+        let x = point[0], y = point[1]
+        
+        xPoints[x, default: [y: 0]][y, default: 0] += 1
+        yPoints[y, default: [x: 0]][x, default: 0] += 1
+    }
+    
+    func count(_ point: [Int]) -> Int {
+        let x = point[0], y = point[1]
+        
+        guard let xEqualPoints = xPoints[x], let yEqualPoints = yPoints[y] else {
+            return 0
+        }
+        
+        var res = 0
+        
+        for (yEqualPointX, firstPointsCount) in yEqualPoints {
+            if x == yEqualPointX {
+                continue
+            }
+            let sideLength = abs(x - yEqualPointX)
+            // check bottom square
+			if let secondPointCount = xEqualPoints[y - sideLength] {
+				if let thirdPointCount = xPoints[yEqualPointX]?[y - sideLength] {
+					res += firstPointsCount * secondPointCount * thirdPointCount
+				}
+			}
+            if let secondPointCount = xEqualPoints[y + sideLength] {
+				if let thirdPointCount = xPoints[yEqualPointX]?[y + sideLength] {
+					res += firstPointsCount * secondPointCount * thirdPointCount
+				}
+			}
+        }
+        
+        return res
+    }
+}
+
+/**
+ * Your DetectSquares object will be instantiated and called as such:
+ * let obj = DetectSquares()
+ * obj.add(point)
+ * let ret_2: Int = obj.count(point)
+ */

Design/GuessWord.swift

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+/**
+ * Question Link: https://leetcode.com/problems/guess-the-word/
+ * Primary idea: Random select a word and check the match count. Filter all words having the same match count.
+ *
+ * Time Complexity: O(n), Space Complexity: O(n)
+ *
+ * // This is the Master's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * class Master {
+ *     public func guess(word: String) -> Int {}
+ * }
+ */
+
+class GuessWord {
+    func findSecretWord(_ words: [String], _ master: Master) {
+        var words = words
+        
+        for i in 0..<30 {
+            let trial = words[words.count / 2]
+            let count = master.guess(trial)
+            
+            if count == 6 {
+                return
+            }
+            
+            var possibilities = [String]()
+            for word in words {
+                if matchCount(trial, word) == count {
+                    possibilities.append(word)
+                }
+            }
+            words = possibilities
+        }
+        
+    }
+    
+    private func matchCount(_ wordA: String, _ wordB: String) -> Int {
+        var res = 0
+    
+        for (charA, charB) in zip(wordA, wordB) {
+            if charA == charB {
+                res += 1
+            }
+        }
+        
+        return res
+    }
+}